Oh, I'm so sorry this happened to you. I'm sure I wouldn't have said anything either because I never want to make waves and I probably would have been too embarrassed to say anything in person. To me it's easier to handle these types of things over the phone. Good luck. "Fat" and any other word that implies it are considered bad words in my house. My BIL thinks that I'm censoring my kids and he makes sure to say all of the "bad words" when he's over.
I'm proud of my girls though, they've never intentionally hurt anyone's feelings and I've never had to be embarrassed in public by them asking why someone's so fat. Sounds like this nurse needs to go to manners school. I'm sure your doctor has no idea how she treats people and he's probably lost patients before due to her rude behavior. Her comments could lead some people to eating disorders or even suicide if they have low enough self-esteem. She definitely needs to find a new job.