Most likely she wouldn't have to pay anything. The insurance company could choose to go to court, but because it's an accident and she wasnt doing it on purpose, or anything that wasnt normal to bowling (throwing, while failing, a ball down the alley) they most likely wouldn't. Also since she probably wouldn't have the funds to pay, they likely wouldnt go after damages even if they felt they had a case.

It's part of running a business and why businesses require insurance. She could have released the ball on her backswing by accident and hit someone in the head causing a serious brain injury. The businesses liability insurance would still play for the damages, and personal injury claims can get into the millions.