How can I convince my friend that she’s not a sl-t and get her to stop crying???

If your serious about liking her and your friendship towards her shows you are. Next time she comes over, use that money to take her out on the town. Plan something romantic where you and her can relax and enjoy the evening. Don't say nothing about or the 'incident' and see where it goes. If she sees that a boy wants to take her out just to have a good nice night and 'if' she freely chooses to sleep with you after that then she has made a choice and should not be traumatized. It also takes care of the money problem. Also if you don't want to do it yourself, find a "good guy" who is a friend and set her up with him and if he is honest then there should be not problem. I hope she feels better soon.