What's wrong with my Rose Hair Tarantula? PLEASE HELP?

When I woke up this morning my Chilean Rose Hair Tarantula was sitting on the floor of her enclosure. Her abdomen was resting against the ground and two of her legs were folded under her. I was terrified, and I thought she was dead. She wasn't, but she was jittery and clearly unhappy. She has plenty of food and water. What could be wrong?!