You are right, it is a lame question.
Act of revenge. <evil> (Different than vengence)
Did the punishment, death in this case, fit the crime? He betrayed her, but is all betrayal deserving of death? In this case two deaths. <no in both cases> In today's society this is considered manslaughter and not murder. There was no premeditation on her part. Murder in this sense implies some forethought or planning.
Was it her place to be judge, jury, and executioner? Who gave her the right to life?
Murdering in front of the daughter, I don't know what level the therapist is going to have to be in order to help the daughter, but it's gotta be pretty high.
Selfishness. She was so hurt by the betrayal but never stopped to think what effect all this would have on her daughter.
So the choices are extremely evil or not extremely evil. I would say extremely evil. Being a cleric, she could have cursed them both or done a lot of other things.