[thelibrarian]

FYI, dietician > nutritionist. Dietician is a protected term, like doctor, or dentist. Nutritionist is not. Any joker can call themselves a nutritionist.

Going to see a nutritionist rather than a dietician is like going to see a toothiologist rather than a dentist.

So it is rather an insult to your sister to say that she is "not even a nutritionist".