Motor vehicle laws expect you to be responsible for your vehicle. Sucks, because if you have to swerve to avoid a head on collision and wrap your car around a tree, you're at fault.
The only way I'm thinking he could be charged with causing the accident is if he actually hit her, causing her to lose control. In that case his action would have directly caused loss of control. As you described the accident, he probably didn't hit her, and therefore he probably can't be held liable for her accident.