Well, do you still actually like her or are you just telling yourself you don't? It's not fair to her if you're still trying to be her friend when you have a romantic attraction to her, and she doesn't want to be in a relationship.
If you have genuinely moved beyond such romantic affections, and still want to remain her friend, then you can try telling her that you've moved on and you can be friends again. If she accepts that, you have to be serious. So if you went above and beyond for her before just to try to win her affections over (maybe always giving her a ride, extra nice things, and so on) that you don't do for others, then you need to stop that. If you stop that and she gets mad over that (we're getting into a lot of what ifs here but I'm just being comprehensive), then that means she just liked having a friend that fawned over her and you're better off without that friendship.
The reason most women will hate being surprised like that is because it makes them question the history of your relationship. Was he being nice to me because he was my friend? Or just because he wanted to get into my pants? It can seem like a breach of trust to them.
You might have to accept there's no way to salvage the relationship even if you do everything right, because some people just won't be able to get over it. There's a fine line to walk here and you can accidentally cross it based on her just interpreting things wrongly.
It can be quite easy, and fair of her, to interpret a strong push from you wanting to be her friend again as you hoping to just be around her again because you still like her.
If possible, hang out with her in group settings. She may be uneasy with one-on-one contact, whether that be hanging out together or personal texting. If you can be at parties with her, or hang out with her in a big group, then that could help her feel comfortable with you again and allow you to build back that trust with her. And if you do get that opportunity, do not put too much attention on her. Just treat her like anyone else there, and don't make it seem like you're nursing a crush on her by paying too much attention to her, or trying to win her over.
It is a very fine line to walk, because any emotional spilling that demonstrates how much you still want to be her friend can to her seem like you're still having a crazy crush on her and she can't trust you as a friend again.
It might help to pretend like you're starting from scratch again with your friendship - it is impossible for you two to just pick it up where you left it.
I remember reading a case about an amnesiac woman, and how freaked out she was when this guy (her husband) showed all this affection to her. She didn't know this guy, and so it creeped her out even though she was in love with him before. So the guy figures it out, and basically starts "dating" her again, treating her like he just met her and is trying to woo her over again. So you might have to do the same with your friend (and obviously not in a romantic way as the husband did), in trying to begin from a clean slate, instead of thinking you can just pick up where you left off.