What can i do about my fiance's nutritionist ?

my fiance wanted to lose some weight, so we went to this nutrisionist consultory,.. she was very nice and she give a survey to my fiance just to know about why she wants to lose weight and about her health story,.. my fiance is diabetic and she is 24 years old,.. the nutritionist presscribed her a drug called phendimetrisine, but it was so weird when she said that it doesnt matter if my fiance is diabetic, she started taking this drug las saturday and then she started to feel bad, we find in internet that this drug is not for diabetics and it is very strong and make you lose apetite, my fiance is not taking the pills anymore what can we do about this and about the nutritionist ??