your friend's car insurance should be responsible for them based on the police coverage. After that, you should pay for the rest.
When you sit beside a learner, you are responsibe for that. Did you read the trafic law of GA? It says that a learning permit guy who can not drive unless there is a driver who has a certain age and experience sit beside him, the driver who sit on the passager seat should be responsibe for the learner. So, that is why I never let anyone whom I did not teach to drive the car in the city street. Also, I encourage the learner to go to driving school instead of being taught by someone having not certificate. Actually, many Chinese guy who learn how to drive in US like to be a teacher, that is not good unless you graduated from China driving school.