Tiffany Thornton and Demi Lovato Tiffany Thornton and Demi Lovato

Did Demi Lovato need a shoulder to cry on after she broke up with Joe Jonas?

"Demi is a strong person — I've never seen her in any 'woe is me' moment," Tiffany Thornton, Lovato's Sonny with a Chance costar tells

Watch full episodes of Sonny With a Chance

Thornton, 24, says she and Lovato, who play castmates on Sonny's show within a show show, So Random!, are like sisters. In the video below, Thornton talks about her friendship with Lovato, her favorite Sonny guest stars and how she's planning her wedding while starring on Disney's hit show.

Sonny with a Chance airs Sundays at 8/7c on Disney Channel.