She was friends with Lori, a fellow animator. They bought some expensive special pencils and promised to use them only for special projects and to ask each other first. However, both of them did use the pencils quite a bit.
When Lori was turned evil by Neflite, Cassie told Amy something was wrong, and fainted when the Gemini Warriors appeared (thus preventing her from seeing Serena, Amy, and Raye transform to destroy them). Afterward, she and Lori promised to be friends forever.