I wouldn't be too upset with the vet for recommend Science Diet.
They don't get much nutritional training and lots of vets prefer this food.
I would just do your own thing and hope the vet understands.
If they continue to pressure you into feeding it, I'd switch vets.
As for nutrical, when she is having those kinds of symptoms, she needs it.
Did the vet say don't give it or the staff?
if the staff said it I'd ignore them and only ask the vet those kinds of questions. If the vet wasn't worried about those symptoms and didn't think she needed sugar, I'd find a new vet...