Everyone so far has had a lot of good comments. Follow their advice. No point in having punctuation and formatting errors drag down your work, after all. So pick up a copy of your favorite book and observe how everything's punctuated, formatted, etc., and do the same. Also study how the author of this favorite book handles dialogue, italicized thoughts, and indirect thoughts. Make like a mirror and reflect.
And now onto what you wanted me to look at.
Plot. This is only a first chapter, so I can't say much for plot right now. I'll read the second and give you a better answer. What I can tell you is that you're going to have to distance yourself from every other story out there with first person female narratives of teenagers. You mentioned something about fantasy, which is perhaps a good start, but if you're even remotely thinking about some sort of plotline that takes a group of bitchy girls and, thoughout the course of the book, teaches them to like and respect one another... This may be my inner chick flick/chick lit hater talking (and I should tell you right now that I bolt from the majority of books like this) but, be careful. The basic premise you have is fine, but make sure it's going in a positive direction. But more on that later.
For now, dialogue and characters. You've got guts for tackling what I'm sure most would consider something difficult, writing in a close narrative of someone of the opposite sex. But I think you're stressing yourself out too much about it, trying too hard, and the result isn't four believably female characters.
You may not know how the female mind works, and in the real world you may be completely helpless--but you're the author, and these four are your characters. You don't need to know how women think; you need to know how Samantha thinks, how Amy thinks. Forcing typical female attributes into their speech doesn't help at all. Because, while of course some girls are complete and absolute bitches, some are absolute sweethearts who never had a vindictive thought in their lives. If these four are bitchy, shallow, petty humans--then write them as bitchy, shallow, petty humans. But write them as humans. Unique entities first. "Amy's a girl, so therefore she must think like X" is only going to steer you down the wrong path.
You do have to consider how being female has factored into these girls' lives, though. The sociocultural pressures on girls and women are different than those on guys. You hear about it all the time in the media, usually with girls and their weight and the new Western obsession with being rail thin, but all you really have to do is watch the commercials on the television. Those'll tell you what society thinks of as 'man' and as 'woman.' Observe, reflect on how that affects your character, but don't make the mistake of generalizing.
And so... that's what I've got to say. All my opinion, of course, take it or leave it at your own discretion.
Rach
