How should a triad approach a topic when two people have an issue with the third person without ganging up on them?
MFF polyfidelitous triad here (meaning the three of us are in a closed relationship).
My longer-term girlfriend's ex-girlfriend is close with us. Most would say way too close, especially considering that early on, she tried to end our relationship (before we were in a triad). Their relationship ended due to borderline abuse, and she once sent me revenge porn, although the ex has turned over a new leaf (got clean from an addiction) and I'm trying to be supportive of her, because I know she still matters to my gf. We just spent the weekend at her cabin, which is fine, she was trying to pay us back for letting her stay with us for a week-ish after a medical procedure.
...But, both my shorter-term girlfriend and I are seeing signs the ex is still in love with her, and our girlfriend isn't doing a great job of setting boundaries. Like, she already committed us all to yet another vacation with her, while the three of us don't have anything scheduled between just us. We have our own relationship group chat... and for some reason also a group chat with the ex. We see her on average at least once a week. Neither my longer-term girlfriend, nor the ex have a lot of other friends, and no family living nearby.
My shorter-term girlfriend and I had a conversation this morning, and while we both feel this is one-sided, and it's almost certain there's no infidelity going on, we're both trying to decide if we should address this and draw a line in the sand about setting firmer boundaries.
But, I'm worried about us piling on and ambushing her. We've only all been living together for 7 and a half months or so, officially in this triad, although this has been some form of a relationship for what's getting closer and closer to two years. My longer-term girlfriend is pretty sensitive, but we really never have had a real fight. I guess I'm not sure if we're picking the right battle, and how to not gang up on her.
The last thing to add is that the ex has told me I'm one of the few people in her life she trusts and that forgave her for being such a shitty person while she was an addict, so I kinda feel like a dick.
Any suggestions here?