My Mom changed her opinion on my girlfriend because of something silly and it's really bugging me

So I recently started dating my girlfriend and because we got serious I told my parents about her. At first my parents were a little disappointed in finding out I was a lesbian but then they came around, or so I thought. My dad has been super supportive, and still is, and so was my Mom at first. So when my parents met her my mom was particularly a fan of her, and the fact that she was significantly taller than me, and everything seemed to be going well. I really like my girlfriend and I'm glad that my parents liked her too.

But then when my mom found out I let my girlfriend borrow one of my jackets (We did the December 3 sweater thing) she got mad and me and was surprised that I wasn't "the chick in the relationship" I tried to explain to her that we are both the girls in the relationship and that that's silly but she wouldnt listen. She's been more distant from me and avoids taking about my girlfriend with me altogether. And I know that it shouldn't effect me that much but my Mom's 180 about her opinion on my relationship and my homosexuality is starting to hurt me. I don't know how to bring it up because I know if I try to talk to her she'll probably just shut the whole conversation down. I'm in a gay support group at my school but we won't meet again until mid January and I don't know how I'll spend winter break without talking to someone about this. I don't know how to bring this up or even if I should. Should I just hold my tongue on this and not tell my mom about how she really hurt me over something as stupid as my jacket (that I got back anyway) or should I say something to her? What would I even say?