She had acrophobia so she found another way to get high
Caitlyn Gilbert was always with her sister, Elena. They always protected each other. After there parents death they both drifted apart, Caitlyn turned to drugs and sex to take away the pain where as Elena wrote. No one but Elena cared for Caitlyn and now no one does. When they are kidnapped at the masquerade party, they meet Elijah Mikealson. Elena escapes but leaves Caitlyn behind for Elijah. Caitlyn has no choice but to go with him, and she warms up to him a bit. Maybe someone does care for Caitlyn after all.
[season 2 - ?]