J.,
It sounds like something is really wrong with your daughter. She is crying out for some attention that she feels she is lacking. I would seek some counseling soon if you are going to keep seeing this man. Give her a chance to vent through a third party, not a family member or clergy, but someone she knows is indifferent in this situation. A professional whom she can tell anything to and know her confidence will not be broken. (Trust is so fragile with children this age.)
I dealt with a situation similar to this in my daughter's school last year like this, due to a situation that arose. Children can sometimes act out in ways that are not always good. Ask the boyfriend to give you some time and not spend the night until you know she is ready. If he really loves you, he will understand and appreciate you putting your daughter first. And seek out the therapist. You will be glad you did! You may even get to know your daughter better and I know you will be glad of that, due to the fact she only has two years left before she is an official "teenager!"
Good luck. And just remember, she wouldn't do this type of behaivor if there wasn't good reason to. She is crying out for help. Hang in there!
Sincerely,
Lee