In truth Cristina probably wouldn't have spoken like that to Colleen when she was first in the infirmary, she had felt conflicted about taking the girls leg even though it had been the only course of action to save her life.
Watching Colleen sit down and work through everything in her head, she could have done tests but Cristina wasn't the sort to panda to people's whim's, no matter who they were.
"It's not exactly a cure but once you learn to you manage them it could be that they won't bother you again" Cristina replied, "You're aware now that what's happening isn't heart attack so even that should take some of the edge off" she added, trying for reassurance. As hard as she was Cristina had first hand knowledge of PTSD and how incapacitating and frustrating it could be which made her fractionally softer.