@rangers23,
There are all sorts of reasons why someone might not want a relationship. Maybe she just got out of one. Maybe she thinks taking it to the next level will ruin your friendship. Maybe she doesn't go for your gender. Maybe she doesn't like you that way.
Or it's something else.
Without giving her the third degree, probably the main thing is to assure that it's not that there's no chance whatsoever. E. g. if she's a lesbian, and you're a guy (can't tell from your post), then you're most likely SOL and you'll just have to deal. If it's not like that, then for God's sake don't pressure her (we see a lot of guys here in similar situations, and a lot of them can get pretty heavy-handed). Be kind. Be friendly. Listen to what she's saying.
You might end up saying something like this to her, "I know you don't want to date anyone right now, and I respect that. But when you're ready, I hope you'll give me a chance to change your mind."
Don't persist if you say something like that. It's said, it's on the table, and it doesn't need to be reiterated or repeated.
In the meantime, live your life. Don't pine, don't wait, don't put things on hold. Be friendly to all sorts of people – including other women. Date a few if it comes to that. Not to get her jealous, but to live your life. If she wants to become a part of the good time that your life is, then it'll happen. If not, then maybe you'll be with someone who's better suited to you, and you won't feel like you wasted your time for nothing.