Pretty weak Christian if she thinks God killed her mother as a way "of getting even" for something. People die and it's usually not fair, especially when it's an innocent child. There are thousands of ways the clergy can explain such events, but to blame Christianity for the death is simply stupid.
My dad once stopped attending a parish because the priest (who had been friends with him for years) said that maybe my dad's first wife died because of some sin one of them had committed.