My first question was, given the time of day, was she under the influence of alcohol?
Several recommendations are to remove your seatbelt first. In aircraft dunking training, that is a no, no, and you want to say strapped in until you are ready to egress. It seems like tempered glass is going to be easier to break, and that tempered glass is more common in rear side windows. Was there a technical reason she couldn't lower her windows or open her door as soon as the vehicle started going into the water?