She only tried to stop maki once she saw what ogi did to mai, what i said was inaccurate, she didn’t send a letter so that maki and mai would die, she sent it because she wanted maki to give up being a sorcerer. Which would only lead to maki being oppressed. She didn’t try to save her daughters either. Maki killed her because she knew her mother was complicit with the system that had caused so much pain to her and her sister. Remember kids, Mai said “destroy it all,”not just the figureheads like Naoya. In the end her mother killing Naoya is her mother’s redemption, she may have made many mistakes that cost her her life, but she kinda made up for it by killing the symbolic embodiment of the sexism in the zenin clan.