I'm a historian with a Jewish husband, so I've considered this scenario, or something like it, many times.
My husband says he'd do anything to prevent Hitler's birth and rise to power, so he'd kill Hitler's mother. In his view, that one death would mean saving millions more lives and not just Jewish lives.
However, I think it would be a bad idea to monkey around with history. You cannot know the consequences, which could end up being even worse than World War II and the Holocaust. No, I wouldn't kill Frau Hitler.