Legion20
I think she'll be alright with it. He's done so many worse things as Lith than he ever did as Derek. Not to mention it couldn't be more obvious that he truly cares about her and his family. She came into his life at a point where this knowledge wouldn't impact her nearly as much as his family. This whole thing is probably what's keeping his life force from healing. Once he accepts this and his abomination, he'll finally be able to advance and be healed.