Hi Matt, you're right, the first example is more grammatically correct than the second, but most native English speakers would have no problem with the second version since we would assume that you are talking about someone who is still alive and still bad and not be bothered by the mismatched verb tenses. In fact, most people would probably also assume that the person you are talking about in the first version is probably still alive and that the past tense is more about when you warned her about him and less about the state of his existence at the moment. Hope that helps.