It's highly unlikely you would be able to win her over at this point. Once a woman has made up her mind that she's not interested or that you're just a friend, it becomes a turn-off if you continue to try. It's as though you weren't listening to what she wanted. Having you chase us at that point is just annoying. I did end up changing my mind about the guy who's now my husband after he'd liked me for a while before. It actually helped that he wasn't chasing me anymore. He was just lucky that I got older and changed what I was looking for in a guy. If he had tried to win me over or even waited around for me, I would probably have been less interested in him.
She's okay with still being your friend because she can ignore your feelings and just enjoy the friendship. She's not the one with the strong feelings or the frequent thoughts, so your feelings are much less of a burden to her than they are to you. You need to decide if you can be happy being just her friend, or if you are happier without her in your life. Base the decision on what's best for you. Don't worry about her feelings when you make the decision because hers aren't as strong.
“This planet has - or rather had - a problem, which was this: most of the people living on it were unhappy for pretty much of the time. Many solutions were suggested for this problem, but most of these were largely concerned with the movement of small green pieces of paper, which was odd because on the whole it wasn't the small green pieces of paper that were unhappy.” ― Douglas Adams, The Hitchhiker's Guide to the Galaxy