Writing.Com General Discussion

I'm working on my second book and the MC goes through a very traumatic experience (she inadvertently kills her mother). I want this to push her over into the darker side of herself, making her do things she normally wouldn't and behave in a darker way.
My concern is that she will come off as too dark by the end of her book and won't be able to pull herself back. I dont want her to end as this dark, hopeless person.
Are there things I can have her do that will keep her from becoming 'unsaveable' but still give her that dark edge?
I dont want her to seem dark, dark, dark, dark, then the end of the book comes, she saves her sister and oh, hey, look how unbroken and happy she is. Thats not fun or realistic.
The point of this story is terrible things can happen and you can even do terrible things but you can always come back from that. There is always hope.

I hope my concern makes sense :/