Your fish likely has a damaged swim bladder. It is a sac inside the stomach area that helps maintain balance and proper bouyancy. These fish don't play dead. The swim bladder could be damaged due to exposure to too much ammonia and/or other toxins in the tank or possibly due to parasite. I don't think there is anything you can do --- if she can eat and survive, then she may be OK, but my guess is that she'll eventually die.