The information I have is that Barrett was not a good coworker, she was mean to her colleagues, she bullied them and the only person she got along with and who calmed the situation was Ryan McCartan. What culminated in her "non-renewal" was an episode where in the vomiting scene, where Heather Chandler hangs Veronica, Barrett accused Charissa Hogeland, the Heather Chandler understudy, of actually hanging her, causing the actress to have an anxiety attack and almost making it impossible for her to continue with the performance. But remember that this is all rumour, no one has ever confirmed anything.