So, she was hung from a tree? Does that mean she has rope burn scars from the event? Does she wear the noose or is it just a memento she keeps in her pack? I also notice a lack of a physical description, how would a random person on the street describe her?
As for the build: I would go with Toll the Dead instead of Firebolt. It's a more "creepy" spell, that invokes the themes of judgement and fate. It would fit this character like a glove.
I like the backstory and thought put into that. I hope the DM ties some of it in with the father and tracking down the mother's killer.
I don't like having 18 in Dex and Int at first level, as well as another pair of 14s. Seems powerful, but that is just me.