She had a kid and a husband to worry about, and an undead being takes a bite out of her kid. Her only options are to have him shot in the brain or leave him to turn.
I do think she shouldn't have committed suicide simply for her husband if not for herself. Not only did he watch his kid get shot in front of him- but his wife, too? You can't stop someone from committing suicide but she at least could have done it someplace private as to not traumatize her husband further... Which makes me sound cold but I'm not. I can relate to her on a smaller scale.