What would you do??

Ok. So my friends cousin is a single parent. She's very nice and cares so much for her child. She's there no matter what as a parents and puts her child's needs before hers. If I had a child I would want to be that kind of parent.  Anyway..... she hasn't been out socially in a year & some months. No social scene or sex. I really don't know how she does it! She asked for one night out & for her mother to baby sit. Her mother screamed and blew up on her? Do you think that's fair of her mother to do such a thing? I really told her to yell back but I don't think that's good advice as a friend? What should I tell her?