We'll admit that following this story has amused us greatly for some twisted reason, but we suspect that humor was not your intended reaction. However, we're always up for helping a fellow writer to improve -- we hope that's what you are, anyway, as opposed to a fantasy-spewing, Jack-struck teenager who thinks that others have an inclination to read her personal stroke fic. Fantasies are healthy; showing it to others with high expectations of praise will only damage your ego.
So we'll assume that you wish to improve your writing skills, because, as this is the Internet, it's your sole medium to represent yourself. Who do you want to sound like: someone who knows what they're doing, or someone who really should step away from the keyboard and never write a word again?
Our general modus operandi is to find some redeeming qualities in a story, not only to lessen the blow of concrit (which we are showing you the respect of assuming you are mature enough to handle, and investing our time in trying to help you improve; we expect equal respect in response, should you choose to), but so that you can focus on your strengths. But it seems to us that no matter how we scour this story, your strongest point is obviously English (though that could use work, we've noticed) ... and that's about it. Good grammar is a solid skill to build on, though, and it's already a head above many on this site.
But there is a difference between grammar and language skills. The first we accept. The second we are not impressed by when it comes to this story. At all. A story is made stronger or weaker by the words with which you choose to tell it, therefore articulation is very important. Naturally, the story itself comes first, but we'll get to that later. We found ourselves bored to tears by the tedious and repetitive narrative. (For one thing, it's always "'Blah-blah,' so and so said as they did whatever." What's with this 'as' stuff? Enough is enough.) Please, give some personality to your character so that we won't confuse her with cardboard, which is especially important if you're going to write in the first person perspective.
On that note, we would advise you NOT to write in first person. At this point in time we feel that your skill level is not apt for, or at least that your style does not warrant, first person narration. We recommend third person omniscient. You can get inside anybody's head and not be switching around, because you never mentioned that Lacy is psychic, yet she's everywhere, all the time, and we found that particularly jarring. If you want a good example of first person omniscient, read The Lovely Bones, by Alice Sebold, but you'll find that her reasoning for that perspective differs widely from yours. That's how it should be done, if ever. This story is not a good example of that style.
Back on the subject of characterization (or the lack thereof), the characters in this story (if we can use the plural form, since they're all basically the same, except for the demon father, which we'll also come back to) are not recognizable to us as the characters whom we came to love watching the movie. People reading fanfiction are doing so largely because the characters left such an impression on them that they felt the need to continue their stories; fanfiction is an extension of the source material, not just original stories which happen to feature characters suspiciously named Mercer. Some people have their own reasons, granted, but that is a very big factor, and if we're basing this story solely on that ... we wouldn't even read past the first line. This is entirely about your character. If this was purely a fantasy then that would be fine, but you chose to share it. Now, some people can make that work, but this story is really in dire need for any connection to the movie it can get.
You should know who your characters are before you write them, and by that we don't just mean their name, appearance, and arbitrary trivia. We mean their lives, their backgrounds, their motivations, their thought processes, their personalities, their quirks, and, if you're lucky, everything ranging from the everyday to the extraordinary. Most of this information won't even make it into the story, which is very important to remember: this information is for your own benefit, so as to be able to craft believable characters (who carry the story, because plot will only get you so far; people identify with characters). In this story you info-dump and you tell before showing; you throw in tons of information that we don't need, have no interest in, and could just as happily do without. It also takes all suspense out of the story. There's no process of learning if we already know everything about a character. There's no intrigue -- the jig is up; the game is over; the puzzle sucked. We want to get to know her -- or, rather, you should WANT us to want to get to know her -- just like any other person we meet.
And this is so important that it needs its own line: ONCE YOU HAVE EXPLAINED SOMETHING, YOU DO NOT NEED TO REPEAT IT AGAIN AND AGAIN UNTIL OUR EYES ACHE. We know her background; stop repeating it every chance you get. Not only is it boring as hell and unnecessary, it doesn't even sound natural, and natural dialogue is a must.
There's really nothing else that we can say about your dialogue except that it's painful for us to read. Work on that, please.
Commas are your friend, by the way. They make you sound like less of a robot. We had to throw that in there.
On that note, we feel the intense need to tell you that, unlike our above statement, rape is not something that you "just figure" you'll "throw into" a story. We can't even begin to tell you how disrespectfully you treated that subject by using it as a plot device and handling it improperly. We also don't care if this section comes across as mean, because we are just that serious when it comes to this subject. We disliked Lacy so much and felt so little for her that we found ourselves rooting for her father. Who cares if a piece of cardboard is being raped and beaten? We cared more about the fact that tears were welding in her eyes, because if your eyes are welding then you need to see a doctor. Seriously.
By the way, can you please explain why Lacy and Jack are not critically dehydrated by now? They never STOP crying the whole way through, and if that's not what you're going for (which it shouldn't be, because we really doubt that it's humanly possible to cry that much), then you shouldn't mention that "tears went down so-and-so's cheeks" every other line. One more thing: IT'S OKAY TO CRY. Really. We promise that if you just say that someone began to cry, no one will hold it against you. Sometimes a tear is just a tear, not a cascading orb, and said tears do not magically appear on someone's cheeks.
We don't think that it was necessary to describe the rape in detail, and we found the entire plot line thoroughly unbelievable, especially Lacy's reaction to it. Case in point: rape victims are not inexplicably made "better" by sleeping with a boy they've known for a few days. We disliked the flashbacks even more; they were lazy and pointless, and you repeated them until your point was long since dead. Also, we don't believe your handling of self-injury for one minute. Re-think that one.
Pacing is next. Why is Jack so bloody protective of her when he's known her literally, what, two days? Again, we command: PACING. That's another one that will make or break a story, and right now it's smashing yours to bits. We just haven't had enough time to care about Lacy or become invested in the story, and you're really not giving us the opportunity simply by turning her into a "woe is me!" spouting, brain-dead girl desperate for being the center of attention with a self-pity complex to rival the sun's mass.
Why is everyone falling all over themselves for her? Don't argue that she's not perfect because she's had it rough -- au contraire, that tough past makes her sympathetic enough for everyone to feel sorry for her. Only we don't see why they should, because none of these characters have had it easy and they've all seen quite a bit for their years. The fact that they're mooning over this obvious Mary-Sue quite frankly makes us laugh hysterically, but only if we distance ourselves and remember that the Bobby slamming his fist onto counters and saying, "He will pay!" is not the Bobby we know, because then we'd cry even more than Lacy.
Why is Bobby always hanging around? Why do Jerry and Angel hardly exist? Why does Lacy spot a picture of them on the mantle and assume that Jack has two more brothers? Why does Jack help her do everything -- can't she stand up by her own damn self? Why is she suddenly cutting herself? WHY? Lots of questions that you leave unanswered, and not to build interest, but because you likely haven't even realized that they're there. And the puppy ... What the hell?
We found it interesting at first that the father was so controlling, but when the abuse came to light (as we expected it to, and in just the poorly-timed way that so often happens in stories such as this) we had to roll our eyes. The entire story is so full of cliches that we weren't sure if it was even for real. Abuse happens -- it's a very sad reality, but our world is flawed -- but usually not just because the abuser is a psychopath and likes to see people suffer. Why does he abuse her? You don't have to condone or like his reasoning, and you don't have to be sympathetic to him, but respect that he has it; people rationalize in their own minds all sorts of things that may be sick and twisted, but are nonetheless satisfactory to them. Few people see themselves as truly bad and have no problems with that. If he's there purely to be a catalyst in the story then we think that you need to step back and consider that everything is not black and white. There are two sides to everything. Few people are utterly evil. What was the significance of his having killed his wife? Just to make us hate him more? Because it didn't work. It only made us grit our teeth even tighter. If you work on that, we promise not to send you our dentist bill.
Finally, because we just don't have the time to point out everything in this story that needs work (so we chose a few to latch onto), we firmly suggest that you find a beta. Not only will he/she catch technical mistakes, but he/she will make your writing sound much better and make much more sense, provided you're willing to work with him/her. If you're lucky and you can find one who works well with you, you may even find a good friend, and hopefully you'll be able to develop your writing skills. Always practice if it's something that you truly have an interest in. If it's not, then we'd appreciate if you'd keep your fantasies where they belong: to be enjoyed in the privacy of your own mind. Hopefully we've made you think and take a good look at your story.