I Would be Liking Some Advice?

Okay, so the other night, some things blew up over the internet(I won't go into too much detail).
This girl has never liked me and she keeps saying things about me and my friends. I retaliate to it and nothing gets resolved because we're both stubborn as a mule.

So she said that my school picture was 'horrendous', this got back to me via my good friend Ethan 'cause he tells me what she says about me in English and Art.
I go online and tell her I heard what she had said and that she isn't a stunner herself.
She says that I'm a gypsy, I'm as wide as a house, I think I'm hard, I'm a wannabe scene kid, I'm stuck up and all I do is sit at the computer and eat, evidently.
I say that she wears way too much makeup, she thinks she's so elite, she has a shit personality, she's an artard, she's so far up herself she can see her dinner, she's a bitch, she's a liar(She was saying my Friends bitch all of the time when they don't even like her themselves) and that most people don't like her at all.

The worst comment made on behalf of her friend was:
"If she picked up her chins from the floor, got lipo, picked up her forehead etc. she would see how gorgeous you really are compared to her."

This girl had NOTHING to do with the argument but she had to stick her nose in.

So a few days pass and my Mum has a word with her and she said that I didn't know her and she didn't know me, so why make comments, people are stirring and something else I can't remember.
She says her Mum said the same and that it was just stupid or something.
Now I hear she wants to apologize and hear nothing more.

After all of the personal comments passed on to me, I don't brush things off easily. I get told things and they get to me. If it's just a small comment, I don't care, but things as she was saying were disgusting. And to be honest, I don't want to apologize. I didn't say half as bad things as she did and I don't feel like I forgive her, because I don't. And she'd probably still talk about me after this.
Should I just suck it up, even though I can still remember all of those comments and apologize? Or should I tell her that she took it too far and that I don't forgive her?

Also, I told Ethan(the messenger) not to mention me in art or English, or tell me anything she says because I will blow up at her and I don't want to hear any more comment like that. But I know he will still mention me, how do I get him to stop? I really cannot take any more shit from these people, I will drive myself insane.
Sorry it's long, had to get the vitals in there.
Bye .xo