Background: My partner and I had Ooened up our relationship back in mid June and we both ended up matching with the same girl. We had a great first date all together but then it went down hill. Then next time we had hung out we had a threesome and they did an intimate thing together…yes that was on my partner for not including me but something was off because why was the girl just starting at me while the act was happening?…. Then we started hanging out with her separately… but any time I’d hangout with the girl she would talk about my partner…a lot…. Then before she left for a month long trip I went over to hangout and she kept yapping to me about intimate details my partner and her did… holding her thigh, making out in public, bitting her nipples… and after that night we had put a soft close on the relationship. I felt like I was losing my mind but just because she was doing these things but because I was dismissing myself of these red flags, because I was desperate for her to like me back… but also because this is all new and I’m seeing my partner fall for this person… after a few weeks of just talking to her as friends (both my partner and I) and after doing heavy research on polyamory and working on managing my mental health, I felt ready for us to go back into it. I told the girl I wanted to start over and that I felt like I wasn’t being my complete self and fear was clouding my judgement and she had said she was excited to see the me that I am and she was wanting to hangout…but when it came to when she came back she only made plans with my partner…and my partner forgot to mention it was our year and half anniversary… so to compromise she canceled their evening plans so she could still stake me out on a date but still got to spend the day with her…I struggles a lot on this day because not only had the girl been acting more distant and shallow with me, she just stopped messaging me completely… I did find out later that my partner had told her I was struggling and had a rough time with them hangout… still no text or anything just straight up ignored me all day then the next day she was snapping like nothing happened…yes I went along with it because again I was desperate for her to like me back, and I wanted this connection to work…. Fast forward to today… after being weird and not snapping me for a day then snapping me like normal and doing that pattern… she snapped me all day showing off the hickies my partner had left…. I was livid. I was trying to dismiss myself tho and tell myself that she wasn’t doing it on purpose and that it was on accident…but why tf she keep doing it then? I finally had enough when I got home and I blocked her on everything because why am I keeping someone around who is disrupting my peace. And since I did that I’ve realized all the stuff she had done. I will also say my friends have been telling me for weeks that something wasn’t right with her. And I actually ended up talking to a couple that had matched with her (the girl has a thing for seeking out couples) and they had said they same thing that she would do sketchy things and try to like break the couple up…. But now here’s the thing, because my partner likes the girl, she’s not willing to just stop talking to her no matter how many of these things bothered me or because of how mental I’ve been lately…she ahead to hear the girls side of things. I just think the girl is going to make up excuses and keep playing her little mind games to get my partner to her self. And I can’t do anything about it because it’s not my relationship and it’s ultimately up to my partner on whether or not she believe me. I essentially just have to sit here and watch her be played and I know it’s going to end badly…I have a gut feeling. I don’t want to see my partner get hurt. But at the same time if she dosent want to step away she’s gotta figure it out.

Is there any advice on what I should be doing to support my partner through this? Is there any advice on what I should do for me? I’m just so lost and confused, I’m just also glad I finally was able to see that I wasn’t crazy and that these things I was worried about ended up being true. I just wish my partner saw that too :/