<human>: Can you condense the text into a few key points?

I've been in a relationship with this girl for about 8 months now. The relationship is great and I like being with her. I have my own apartment so we usually hang out here. One day about two weeks ago we dropped by her house (she lives with her parents) so that she could get changed - no one else was home. I stayed in the entry while she ran upstairs. I was just looking around, waiting for her when I saw her family photo. That was the day that I realised. I never said anything to my girlfriend about it. I guess I felt that if I kept it to myself then it wouldn't become real.

I had been seeing her (mother) for 12 months. Only about 6 months ago I stormed out in the middle of a session because I was frustrated and it had done literally nothing for me - it was just a waste of my time and money. I'm not really sure what to do now. During the 12 months that I had been seeing her, she was easily the closest person in my life, I told her a lot of personal things. Things that I certainly wouldn't want my mother-in-law to know.

My girlfriend, being the pushy person she is (haha), set up a dinner for Monday night. I should tell my girlfriend before I meet her family, right? I don't really know how to deal with this. Do I alert her mother beforehand? I was thinking of booking a session sometime before Monday so that I can talk with her about it. Is that a bad idea? I'm asking because I want to know the best way to deal with "meeting" her, but I also need some personal advice because I find the whole situation to be extremely uncomfortable. 

--I was seeing her mother for existential depression and anhedonia.
<bot>: My [M19] girlfriend [F19]'s mother is my former therapist. She wants me to "meet" her family. Advice?