I doubt that the boyfriend is being completely honest.   The situation described is very typical of the triangulation that is one of the favorite games of narcissistic abusers.   It doesn't prove he is triangulating you with another woman, but, given the resemblance to that behavior, the fact that he states she's "crazy," and you don't know any of his friends, sends up a good sized red flag to me.  They always say the woman they are cheating on is "crazy," or something like that.

My advice is, do not ask him to clear up a confusion he has created.  If he is not being honest about the situation, he will only be dishonest again.  Figure it out for yourself.

Most people who have actually gotten away from a "crazy" ex do not encourage the crazies by keeping a facebook page or anything else showing a continuing relationship, especially if they have concerns. They get restraining orders.   And most people who use that excuse, "my crazy ex will go crazier," are lying.