who was the young woman in flashback?

Was that his Stepmother? I thought earlier when talking about his dead stepbrother he mentioned how his father decided to raise him after his stepmother died because they were close to the same age and would be good for each other. Made me wonder if the father killed her for messing with him, but it was never clear about any of it...

Tundrabeast

I believe it was Caitlin Turner, and, at least from what other posters have said, in the book, she was the nanny.

The whole world is a very narrow bridge. The key is to be fearless. R' Nachman of Breslov