Can you see how getting comfort from your therapist while puking could/would reinforce that behavior? I know if i thought a behavior of mine would result in comforting from my T, I would probably want to do it all the time. I don't think she should have followed you into the bathroom though. That can also be reinforcing. Both positive and negative reinforcers. It's better (imo, of course) to not do anything. You are the one responsible for your own behaviors. Do you want to stop the behavior? Why not focus on what causes it, the triggers, and what you can do to help yourself NOT do it?

Another thought: Did you tell her you wanted to puke to see if she would really comfort you like she said?