Like most friends with benefits, one partner always wants more, that's you. She doesn't, and you can't handle that. That's your problem, not hers.
can someone give me advice on how to get her in to a relationship...
She doesn't want one, at least not now, and its doubtful she will change her mind, but who can see what the future brings.
also advice on how to let go... I would like two answers kind of like a ying yang..
Stop having sex with her, and she will probably go elsewhere for her fun.
Its up to you to make a decision, and the right adjustments that work for you.
A lot of guys would be wondering what your problem is. I don't, you want the whole package, but she doesn't.
Its not an easy choice, but its all yours. The last thing you need is to keep digging yourself in deeper with no clear prospects, but hey, you can always enjoy what you have, and see what happens next.
Who knows as your lust may just wear off on its own. Or hers will. Is she worth the risks or not?