devilish suitor
A lot of times, a parent will abuse one child but not the other, or one gender of offspring but not the other. If she saw the daughters as "cash cows" or to be even more armchair psych about it, a way to relive her own dreams of girlhood, she may have left the brother alone. Or maybe he's as big a douche as the mother and thought it was fine to treat the sisters like that. The mother is claiming she was just trying to stop the girl from having sex with her 18 yo bf but so many people coming out and saying no, the woman was abusive and they saw her doing it makes me think the claims against her have some weight.