I've just read through this whole thread for the first time. To me, it sounds like the original question has actually been answered and even the fact that this thread has been going on for a while might indicate that your benefit from asking is to explore why it is important for you to ask/know. What if you don't can't access that info, how does that affect your therapy or feelings about her? Might be simply why the T asked you to think about it in the first place and you clearly have thought about it quite a bit. Is it possible that this is actually enough and knowing about her bf is not really the main thing here?