The peeps recommending cooling blankets and window units for her have the right idea. Most of the misery is lack off sleep. Waking up soaking wet and having to shower and change only for it to happen again after you finally drift off is a beating that would make most of you fucks cry like little bitches. The mood swings weren't too bad for me but I'm an asshole normally so I was more myself, if anything.
Saying something like, "I'm so sorry you are going through this, it hurts me to see you so miserable... nobody deserves that." when she says a mean thing might catch her off guard and buy you time to make your escape. But more importantly, it might help her to think about working through things differently instead of making you the target of her ire.
She'll come out of this and if you've been a supportive nice guy through this, it will likely earn you brownie points big time.
There are a couple of guys with their experiences and how they were supportive that makes me want to suck their dicks. I'm sure their ladies show how appreciative they are. Just saying.