Maybe I should clairify: I don't remember if it was ever definitively shown which woman was driving. I think I remember Claire saying her mother was driving, but that there was a very loaded close-up of Claire looking really guilty. Doesn't she also apologize in her last visit w/her comatose mom just before she gets on Oceanic 815? She apologized for putting her mother in the hospital for the last several years and for the fact that she would probably never wake up.