From what you have described, it sounds like your mother is disordered and most likely has her own history of being neglected. It sounds like any situation that asks "her" to nurture is a trigger to her and she gets resentful and angry and exhibits reactions where she turns things around to "her" being the victim in some way. The fact that she uses your brother to complain to and vent to is showing how she never really matured and gets angry when she feels her needs are not being met. She probably is suffering from low self esteem.

As you learn how to recognize her behaviors that are unhealthy and learn to not engage her, but also not to expect something she cannot give you as well, you can make gains. Understanding that her toxic behaviors have no bearing on your worth as a person can provide you with your own space to develop your self and sense of self worth in spite of her "lacks". Yes, your symptoms of depression can be reduced as you learn how you can actually gain in spite of your mother's behaviors that never contributed to your sense of self esteem.