The movie is about a girl who see's her mother killed but does not remember by whom. The killer ends up being a friend of the family who was interested in the father. It is an older film from possibly the 40's or 50's.

Can you remember anymore details?

I think the young girl ends up in an institution and something the woman does triggers her memory and she then knows it was her that killed her mother. It is a pretty foggy memory but that's about it.