She sounds like she hasn't figured out exactly how to say divorce just yet, like she needs to work on how to say it. because everything else she is doing says she wants one. moving to her sister's house, talking about getting her own place there, obviously flirting with the salesperson in front of you and getting information in case she wants to go out and party.
It's not fair for her to keep telling you to stay where you are while she gets on with whatever agenda she has.

When my ex and I first separated, we were still in the same house and I agreed to counseling for 2 months to see where we were at that point. Unfortunately it didn't work out (we'd tried 5 times in 8 years)

If she's been gone over a month with no efforts whatsoever to try and work on things with you and barely contacting you then you need to get better clarification from her of her intentions. You might also contact a lawyer to at least get some idea of what you need to do to first protect yourself and to find out what has to be done if you do end up going the divorce route.

If not for her behavior, I would have given her the benefit of the doubt when it comes to a nervous breakdown. I had my first one about 10 years ago and it involved an ER visit...when we attempted couple counseling while I was in this state, the counselor told us I needed to get myself together before he and I could come together. So, I don't know just how bad her 'breakdown' was. She seems to have gotten over it pretty well seems like.

I am really sorry you are going through all of this and I do wish you the best