I think she may want to see where things go this time and may have realized that she gave a good thing, what you need to do is be very clear as to what you want instead of everything being up to her. Ask her what all of this means and what she expects from you, you want to make sure it isn't a sexual thing and whether she wants to try again. My advice to you is don't lose this chance that you have if you want her back tell her that she may not think you will take her back because of what she did before. All of the sign are there that she wants you back but you have to ask her if it's for sexual reason or if she loves you and wants to have a relationship with you. If you just started back to seeing each other then give it at least a week before having that conversation with her and make sure that when you talk to her it's only you two so that you can really open up to her if you continue to act as if you don't care she will take that as you not wanting her back. If you have anything to add click reply.
It may be best that you take it slowly and not rush things this time. She probably felt like a "tramp" because you just started talking again and already she had slept with you but with your reassurance that it was okay will make her feel a little bit more at ease when it comes to intimacy. You really need to have the talk with her and ask her the questions you want answered like; What is this exactly? Do you want to just be friends? Do you think we could give it another try? and then go into how much you care about her and what you want but allow her to answer your question before telling her how you feel so that you know if you should even tell her how you feel and if her answers sound promising then tell her.