Well, at least that's a little closer to a don't-ask-don't-tell arrangement, which I think most would agree is usually less than ideal but a lot better than straight up sneakery.
It occurrs to me that a major problem I would have in this situation would be that, knowing things aren't worked out between her and her husband, I'd fear that he'd suddenly decide he needed to know what was up and then would demand it to end once she told him. A partner's partner vetoing a relationship is a major fear of mine -- that would just feel so gross and sad to have a break up imposed by the outside. I have *no* reason to think it'll happen in my current situation and the thought *still* freaks me out, so I think I'd not wanna make myself emotionally vulnerable at all if I thought that was more of a threat.
Don't mean to be depressing, just thinking it through...
The major players. Me, 30ish bi female. Gia, girlfriend of 4+ years. Clay, boyfriend/dom. Davis, ex/friend/"it's complicated." Eddie, roommate & fwb.
The supporting cast. Eric, Gia's husband. Bee, Gia and Eric's toddler. Dexter, Gia's lover. Helen, Eric's lover. Izzy and Nikki, Clay's partners. Liam, Eddie's husband.