If you find yourself having the same fight over and over again, despite different circumstances, it may be that this is the way she copes with stress.
She seems to always get angry at you, only to self deprecate once you call her out on her behavior, then you feel bad and apologize.
Afterwards you feel frustrated. Why because you feel had. I think it's really like this.
She acts odd because of her depression, then lashes out at you because of it, you call her out so she does the "oh woe is me" routine to make you look like you are a terrible person, and remove any responsibility and Scrutiny away from her.
It's a defense mechanism. It's how she blocks any pressure to work on herself.
I'm not insinuating that your w is a bad manipulative person. On the contrary she is hurting but is unwilling or scared to deal with it. So she deflects.
The key is in breaking the cycle. When she self hates how about saying
"you're not a bad person, but what you did was wrong/uncalled for/mean"
If she gets upset at that comment just challenge her original action again.
As if to say you can't get mad at me over a promise you broke.
Just repeat that you don't think she is a bad person, but that she made a mistake.
Don't be surprised if she gets very upset, tell her you would like to discuss things but not if you are going to yell at each other.
I think the key point is to stay on topic and remaining calm when she goes into DEFCON 1. Show her that anger is a fruitless communication technique.
Yes anger is a communication technique, just not a very pleasant one.
