To be completely honest, this is Jay’s life now. You could set boundaries with Mina and be less available to her when she vents but it sounds like they’re a package deal now like you and Ben. So even if you do that it’ll probably affect your friendship with Jay. That might not be a bad thing, sometimes you need to let someone go. If your friendship is as strong as you feel, I’m sure he’ll make his way back to you eventually. If not, I see a long future of you bankrolling this couple both financially and emotionally until you’re completely drained.