For everyone who'd like a highlight reel of that instead of reading it:
Cortneigh23: i dont care
OAO3405: You know, you never did tell me what makes me so ugly, anyway.
Cortneigh23: i dont care
...
OAO3405: I was going to say something about the boyfriend comment, but forget it. There's no point.
Cortneigh23: yea cus u dont have ne thing for that one
OAO3405: I was going to counter by basically saying that I'm smarter than you, which in the end will count for a lot more, and could likely get some girl if I really wanted to, but then I realized that would have no effect on your opinion and possibly just make you defend your intelligence.
Cortneigh23: nah i kno im dumb idc..and uh you could never get ne girl you wanted
OAO3405: Yeah, because I'm just so damn picky.
Cortneigh23: no jus because ur so ugly
Cortneigh23: no girl really likes smartness i mean my boyfriend is as dumb as me
Cortneigh23: so i dont really care
Oao, you aren't getting to her at all because she really doesn't think about what you're saying. Despite her typing like a retard, she's proving to be a lot less naive and a lot more grounded than you, whereas you're just trying to get in some good internet insults for you to chuckle at later while you sip a slim-fast. Even if for some reason you were 'killing her from the inside', her boyfriend would just make her feel better and then probably kick your ass. A lot of girls your age are mean to people, and most of them grow out of it, but you can't expect her to act like an adult because she isn't. Maybe in 10 years you can expect a heartfelt apology from her, but probably not even then, as she'll have written off her behavior as part of growing up.
Which you should invest some time in.