I love people being upfront with me about ways I have hurt them. Just tell her that, yes, she did hurt your feelings. And tell her it hurts you when she wants to discuss your relationship with your mother.
I don't see where it has to be that complicated.
I almost always take things at face value. And I appreciate honesty, although I do respond to it better if it is done in a sensitive way (calm voice, appeal to my emotions, without harsh terms or accusations).