What movie is Claire Holt filming?
I think you are talking about 'Blue Like Jazz: The Movie'. She is also currently appearing on Pretty Little Liars & The Vampire Diaries.
she left because: in the show she is supposed to be traveling the world with her parents.and in real life claire holt (emma) was going to film a movie and was suppose to return but since the show did not keep filming after season 3 she never had a chance to come back. bella (the substitute character for emma) was a mermaid since she was 9.