Dear Scr33n0r,
Boy, I kind of know how you feel, I have a girlfriend now, She was totally depressed when I met her and I was JUST getting out of the depression stage... It was extremely hard on me not to think of suicide..etc. She was into the black, cutting herself and all of that I was just getting out of all of that (yet still cutting myself)... She ended up breaking up with me a little after, and our conversation ended with me saying "You're making a big mistake." Two months later, we started talking again, and I asked her to the movies, we made out..etc she said "I understand what you said, you were right I was making a big mistake." She cheated on her boyfriend because she missed me so much, Well I asked her out two days after her breaking up with him. And we went out and we've been
happy ever since (8 months and going.) Now we are both far out of the death music, black clothes and death thought stage and all of that. It's going really good.
My advice to you is to say Yes, and TRY really TRY to stay happy around her, yes, you may have to lie to her...but as long as she sees you being happy, and how much you care for her, she'll become happy, and she'll support you when you're in need too. It's like you both support each other, and that is how a relationship should be.
If you happen to say No to her, try to do it in person so she she doesn't do something stupid (if you say "No" on the phone she may say "This life isn't worth living" and kill herself... :-/") If you say it when you see her she'll probably have more time to calm down.
I know this story wasn't exactly like yours, and I've left stuff out but this is what I did and we're perfect now.
Good Luck Scr33n0r,
Best Wishes.
.
EDIT: Ah, This is what I get for not reading all the posts, He already said yes. haha.