So my Nesting partner has a girlfriend. The two of them have dated and broken up 5 times in 3 years and just got back together again. I have been poly for 3 years now and he has been poly for 4. She has only had one poly relationship before this which went terribly. She has been extremely jealous of me their entire relationship this time around. She keeps saying terrible things about me to him and trying to get him to break up with me. I have been friendly towards her the best that I can. But no matter what I do, I can’t seem to make things civil between us.

I don’t want to ask my partner what he sees in her but I honestly just don’t see it! He’s been on my side defending me against her accusations, but it’s day 4 of 12 hour arguments between the two of them and I can’t help but feel like I’m tearing them apart

Advice?