she just trying to hurt your feelings to get her way!! My oldest son used to do this and it stung so bad till I figured out what he was doing!
My DD said this to me a few times recently, usually when she was in time out!
Later that day I sat with her and explained how much she hurt my feelings and would she like it if said that to her?she said she would be very sad and would never want to make me sad! and she hasn't said it since!!! Thank God!!!