AIO GF makes a joke about me being eskimo bros with her ex
Long story short my gf still maintains a friendship with her ex after their break up years ago. He comes and goes, this time he's in town for a few months and she caught up tonight by grabbing drinks with him.
Another related detail is the ex and his friend group (my gf's former friend group) are hosting a party at their place and so I'll have to go and meet them all eventually for the first time at some point.
Anyways later that evening when she's back she mentions some details about their hangout, and then asks me if I would be down to do anything "for the bit". I asked what is it and she thought it would be funny if I greeted him as my "eskimo bro" and asked if I would do it for the joke. She mentioned she already ran this joke by her ex to see if he would do the same.
I didn't react negatively in the moment but two things made me uncomfortable- one was that she was joking about that earlier when hanging out with her ex, and the second is it feels disrespectful to joke about that but I'm not sure why.
Generally I'm pretty chill and open to joking around but I definitely declined that one because I felt weird about it. She then mentioned that she knew I wouldn't do it because I'm "too shy" (I am but the real reason is I'm uncomfortable) and that she might do it as a joke. I physically just removed myself from the room to chill out because I felt anxious about that. Didn't feel good to hear any of this.
For her sex is something that is not super meaningful and pretty casual, whereas for me it is important and has meaning. I've struggled in the past with her keeping in touch with her ex, also her numerous past casual partners while we dated in the beginning.
She knows this is something I struggled with before, and we've talked about sex and her past many times. I can't tell if I'm overreacting about her remarks because she thinks it's "water under the bridge" and that it's ok to be this light hearted about it. But I have to literally meet the ex in a few weeks at their party and it's a huge step forward for me in trying to get over my past struggles.