Thought this looked familiar, it was a recent decision on a motion in the Superior Court
http://www.canlii.org/en/on/onsc/doc/2010/2010onsc3000/2010onsc3000.html
The judge threw out that part of the lawsuit where it was alleged that the designated driver was supposed to monitor the injured girl's drinking while at the party.
The judge left it to a trial as to any liability or damages based on what happened in the car only.
The case will depend upon things such as;
what did the driver do when she said she was going to jump out.
when did she take off her seatbelt / was it ever done up
was it even safe to stop and pull over even if the driver wanted to
etc etc etc
This is undoubtedly a case between the insurance companies for the driver and the girl.
The people are named as the parties but it is all about the insurance companies figuring out which one of them has to pay her
He has insurance as the car driver; she probably has insurance on her own car and that policy will cover her even though it was not her car and she was not driving. But her company wants the driver's to pay a portion.
This is just standard insurance law and has nothing to do with either him or her trying to get away with anything.