what is the name of the movie when a girl, I think she was played by Winona Ryder, ...?

The girl thinks this woman is her mother and she eventually confronts
the woman and they have a tear-filled scene, well at least on my part,
and the woman tells her no: her real daughter died at birth or
something like that.

I just remember one other scene when she is dressed really geeky and
gets on the schoolbus.

Sorry that's all that I vaguely remember.