It was Colleen's last day at SGMW and she was saying goodbye. She easily said goodbye to Teddy and Callie and hugged them, but she hesitated when she got to Arizona, asking if it was okay if she hugged her while glancing at Callie. When Callie and Arizona both said it was okay if she hugged Arizona, Colleen did so, but lingered, causing Callie, Arizona, and Teddy to stare. Callie then interrogated Arizona until she found out that Arizona and Colleen had had a sexual relationship before Arizona knew Callie.
She and Arizona had a relationship that Arizona described as, "a tiny bit of a thing a very long time ago."
Colleen was a nurse at Seattle Grace Mercy West Hospital. However, she left that job to go "back east."