I agree that a woman can be an abuser. This would be particularly true in a Wizarding World where physical strength would not be as much as an advantage has it is in the Muggle world. But that is not case here. Lily was not the abuser in their relationship.(Said relationship being a friendship)

Snape having to watch his words so he would not use a racial slur around Lily means that Lily is a troubling sign, but more because it shows what Snape thinks of Lily. The fact that she is not happy that he is palling around with other racists does NOT means she is controlling who he sees. A friend can be worried about who her friends hang out if she things said friends are a destructive influence and not have it be abuse. How can.... I was going to say "How can they not understand that?" but then I realized they really, really work at it.