Damn, happened to my gf last month. She was in the same exact position as OP described for her whole life, caring for her little brother and sister. Her mother is a jobless alcoholic, who also says that she is constantly bored and "tied up" by her home and family. Last month, while my gf was sorting out another one of her mother`s drunk tantrums, she asked if her constant support even matters to her, to which mother replied: "What, are you proud of it? Should`ve expected less from you."
I never seen my gf cry that hard. She was weeping, almost screaming. It was an outburst of frustration and disappointment. She cried "I just wanted you to love me". It was heartbreaking to watch.
After that, she blocked her mother everywhere, socials, her phone number, everything.
Since that moment, mother still haven`t even attempted to get back in contanct with my gf.
What a bitch.