Feminism is the idea that women have the natural right to make decisions for their own lives and pursue those decisions to the best of their abilities. Taking part in the detention and mistreatment of a woman is orthogonal to being a feminist.

Idealism, well I'm assuming she's not an adherent of the philosophical kind and aspires to some sort of 'ideal' which I would have a hard time reconciling with slavery.

So in conclusion, I reject your charges of No True Scotsman. Some things are cut-and-dried.