Is OTHER wrong in the post ? POST : Throwaway. My girlfriend are in a huge/ potentially relationship ending argument. I need to know if ITA. 

I’m in a very LDR with basically the girl of my dreams. Absolutely beautiful, smart, driven. Things have been great despite being a several hour plane ride away from each other. 

She came to town, and I was so pumped to introduce her to my friends. They threw a party, and while on the way, GF randomly asked “are there any girls I should be worried about” This is probably where I fucked up,  but I explained that a girl I used to see will likely be there. Explained that we were supportive of each other during our respective divorces, and we hadn’t seen each other since well before I met GF. I was asked if we ever slept together. I said yes, because...we had. Also important to say that we never told out mutual friends about our fling, it wasn’t a big deal. 

Everything started out great. Everyone was so welcoming to gf, including ex who was there with a new guy. 

GF gets drunk and made a comment about single moms dating being weird, almost directly have ex mentioned  her children. She randomly asked why she divorced ex husband...in front of everyone, and then asked, again in front of everyone, where we had gone one dates. I was honestly so surprised. So was everyone else. 

I apologized to ex and her guy as they were leaving, and she said “no worries. Play 23 year old games, win 23 year old prizes” (were all in our 30s) and gf heard this and sobbed in the bathroom for the rest of the night. She was so devastated that I did tell her that was out of line; however, I feel like nearly everything gf said to her was out of line. 

We got into the biggest argument about how I didn’t have the decency to stand up for her. I told her honestly, I should have stood up to ex when gf relentlessly tried to embarrass her, and she can’t be surprised at a little passive aggressiveness after the way she acted. 

She’s now back on a plane, and we will discuss further once she clears her head.

Am I the asshole?