M.P.
I feel you should tell her that you do not drive while talking on the phone and if she is going to be talking on the phone while your daughter is in the car you would rather stop the carpooling which really helps you and her (I hope)and you wish to continue carpooling if at all possible but that is something you do and it is perfectly O.K. if she chooses to continue talking on the phone while driving if that works for her and her family but it is a choice you made for your family. Parents should not be afraid to speak up when it comes to your children and not think whats easier for you but what is best for your child always trust your gut instinct. Make sure your daughter knows to tell you if the mother continues talking on the phone if she agrees to stop even if the mom tells her not to. This will teach your daughter she can always come to you when something is not safe for her. Best of luck to you and your daughter.