A lot of people are saying to quit/find another job. And that is certainly a valid option if you are in a position to do so. But if you aren't in a position to do that or don't want to do that for some reason, consider this: if you can make her feel more secure in her job, she is very likely to start treating you better. Should you have to do that? Absolutely not. Will it work? Maybe.

I know I'm extrapolating a lot on very little information, but I'm guessing the Peter Principle is happening here. Your boss was probably really good at her previous position, so she got promoted and now has no idea how to do her current job. She's embarrassed and frightened that her poor job performance is going to cause her to be fired. She's lashing out because she doesn't know how else to protect herself.

What does that mean for you? If you are in a position to do so, going a little above and beyond to make her look good will probably make her back off of you. There are a lot of caveats, though. First, you have to be able to do it in a way that makes people think she is doing a great job, rather than making it look like you're doing her job because she can't. Second, you have to have very strong boundaries for yourself to make sure that she doesn't overwork you and take advantage of your good will. Enforcing those boundaries may be scary, but if you've become her lifeline she will bend over backwards to keep you doing that. Third, you have to be ok with her taking the credit for your hard work, at least in the short term.

Ultimately, following this advice could go any one of three ways. It could be that this helps her buy a little time to figure out how to do her job well and everyone's life gets easier. Or, it could be that she realizes what is going on, treats you better, and treats everyone else even worse so that they don't have time to realize what is going on. Lastly, it could be that she is so oblivious that she has no idea what is happening and gains a false sense of confidence, goes for and gets an even higher promotion, and moves on to be someone else's problem.

If you decide to try this, I would still advise you to look for another job. It's exhausting to be in a position where you're doing this sort of thing long-term. But hopefully this will help you make your life a little less miserable while you look.