Sorry, but I think you may well be on to something.
There are a number of reasons that this seems like a bad idea to me. Let's focus on #1-- this woman seems to be a drama magnet. Foisted poly on her husband with little to no negotiation with him on the matter (at least that's how it sounds), drama with the new roommates (of course it sounds like it's all their fault from the way she tells it, but there are *always* two sides to these stories), dodging you with sketchy excuses rather then just saying that she's not comfortable hanging out, and now dropping hints to her boyfriend about what she wants for their relationship rather then asking directly.
You and he both need to be very cautious. Whether she's trying to break you up or not, she's trouble.
Me, 30ish bi female, been doing solo poly for roughly 5 years. Gia, Clay, and Pike, my partners. Davis, ex/friend/"it's complicated." Eric, Gia's husband. Bee, Gia and Eric's toddler.