Before we jump all over this person, it's a well known fact that people who have been sufficiently traumatized will do some truly weird stuff when it happens. I'll wait for the evidence to come out before saying anything one way or another.
She cared so little for her son that she drove him around while she was drunk. Sure, he was 29 and should have known better than to get into the car with her--who knows, maybe he was drunk as well. Doesn't let her off the hook for driving drunk.