If shes not in treatment and actively working on helping herself feel better for herself and also for those around me , The I am sorry she is just being abusive and taking advantage of those around her.
It's possible she has more going on than depression.. Bipolar and some personality disorders can cause/explain the anger she is having. Just a thought.
No one here is a Doctor and cant diagnose of course.
Regardless, she has to want to get better, having a mental illness isn't an excuse to treat others terrible.
Welcome to PC