Except for the part where she says she doesn't want to be with you because she prefers women, it sounds like you get along really well and enjoy each other's company.

But you could have a relationship like that with someone who DOES want you.

Staying friends with her will lower your chances of being able to move on. Staying friends is fine for her, because that's all she wants anyway. You want more. You've proven you will never get that from her.

Letting her stay in your life is going to be like trying to run a marathon with cement shoes.