This sounds very much like a girl that I just broke up with. Ask her questions, does she or has she moved from job to job?, was she basically in a relationship when she met you?, has she or is she moving in with you because you want her too or because it would be best for her. Does she ever ask you how your day was and genuinely listens and asks more questions or does she cut you short and talks about all the drama of her day? Her last boyfriend does she still talk to him or did she talk to him till you had to ask her to stop? Trust me she didn't stop she just doesn't have his name in the phone and memorized his phone number. She talks to him when she is away from you and probably still sees him and others. Her stories are to make you feel sorry for her and to comfort her taking your emotions and pulling them all to her. This is the first stage of trapping your heart and making it hers. When you are out is it very important that she is the prettiest most desirable girl in the place and if she isn't feels very uncomfortable? The part about the rape, if she is hpd is just a way of feeling less guilty herself for having sex with this guy/guys. The part about the teacher is probably true but it necessarily was her getting the attention of the teacher cause he was spending time with another student. If a lot of this you can answer yes to then be very careful in the days ahead. If you think she is being unfaithful, lying, manipulative she is believe your gut. I would imagine the sex is great and she is beautiful, that is why it is so hard for you to believe your gut. I bet in the past you would have known and taken the proper actions.
Good luck