How to deal with a pathetic bio mother.

So a little background. We have been in a bitter custody battle with a complete psycho for the past 2 years. My husband won full custody, mother only a few hours visitation once a week allowed. (it says something if a dad wins full custody doesn't it?)

Anyways, she does nothing but trying to make our life hell. She has some serious mental issues and goes from being the nicest person you've ever met to the biggest bitch you've ever met.

I've been always decent, me and her used to get along great. But I don't let somebody push me around either. But all the constant bull shit does affect me mentally and sometimes I don't know how to stay sane considering my husband works crazy hours and is gone a lot and I'm my stepdaughters main care taker.

How do I deal with this? How will I stay sane in a situation like this?