Can a gym be sued if an elderly woman falls off a treadmill because the previous user left it running?

An elderly woman friend had to be ambulanced to a hospital and is still admitted after falling off a treadmill that was left running by the previous user and banging herself up pretty badly. I'm pretty sure gyms have cameras mountd everywhere so everything can be seen on video from the time she walked into the gym. Is the gym negligent? Does she have a case if she sues?