Callus studied with Ian Jewel at the Royal Academy of Music in London, earning an Honorary ARAM (Associate of the RAM).
At age 26, she was appointed to the faculty of the University of Washington, where she taught for seven years before accepting a position at UCSB.
In 2016, she accepted the position of Professor of Viola at Northwestern University's Bienen School of Music.
She has also served as the Viola Forum Editor for the American String Teachers Association Journal, and she founded BRATS (Bratsche Resources And Teaching in the Schools), an educational outreach organization.
Callus has made recordings with several labels, including ASV, Analekta, and Dutton Epoch.