Thanks so much for all of the advice! I apologize for not being more clear about our set up and a few other details. Since I live it, I was trying not to bog things down with lost of details.
Hanna and I where friends at work when I met Issac a few months later. Michael was away at this point and we have been poly for about 5 years. Hanna and Isaac wasn't yet open (and don't have kids for the record), but talking a lot about my views on the subject they decided to try it out. Issac and I started dating and getting serious. Hanna and I messed around a few times, but decided she didn't want to compete with Issac and I's budding relationship. When I suggested to Michael that maybe he gets to know the people I talk so much about, he started talking to Hanna over text. After a while the idea of "grouping up" was brought up as Hanna and Michael started talking about getting serious. They started a LTR while he was away with the expectation of continuing it once he got home. When he came for a month long visit, we all spent lots of time together and decided that the four of us wanted to try becoming a more integrated, blended family.
As far as this issue, after Issac and I talked about it and he said he didn't know what to do but understood what I was saying and we'd work on it. When he got home looking a bit low from the conversation, Hanna got the story and got a bit upset about some of the details that apparently Isaac didn't get and conveyed wrong to her. After a conversation that I made it clear I didn't want to push her out of her own house or take the time she gets with him. She started saying that she just needs to back off and do her thing and if people need her we know where we'd find her. So she's just going to back out completely and not try to get time with Issac. If he needs it, he can come get it. It's frustrating because she is just going to withdraw and essentially become resentful. I keep suggesting a schedule so we can at least know what to expect from the week and I can plan a bit of time to get out of the house and be alone with him. She seems resistant to it (take away from "spontaneity") which I am not sure how her "solution" of withdrawing is better then sacrificing spontaneity.