It does sound awful but you should not have to coexist because it is your house and your husband should be backing you up when she turns nasty and vicious. Is it vicious enough to call the police? You might both have to formally warn her in writing that she will be thrown out on a certain date if she has over the top behaviors that don't change. I thought my situation was hopeless, but it is getting better because my H and I are more united. There are also mental health issues in the mix but that too can be improved with the right help. My recommendation is to talk to him openly about everything. Try not to go over past mistakes, focus on the now. If you are not in agreement then, sadly, things probably won't work out as well.

And I assume our situations aren't exactly alike but I also had to get help for my anxiety, depression and perhaps bipolar 2--I do find that I am a lot more level headed on the medications I am now taking. Don't want to diagnose anyone in your family because I feel like MI diagnosis are tricky because you have to figure out how much is behavior verses personality verses chemical ups and downs that meds can help with. If you are not getting cooperation, all you can do is focus on you and maintain strong boundaries.