I would strongly suggest getting the Endo. If you need your doc's referral... insist on it. They specialize in metabolism and the lovely endocrine system with all its numerous hormones
A Dietician should also be recommended - if not by your doc then the Endo will for sure. The first tests he'll run will be on her thryroid (blood tests).
Sorry, but one A1C test or fasting test does not a diagnosis make (for or against). What was the number anyway? I'm curious what your (questionable) doctor has determined is "normal". That her insulin levels are "extremely high", might suggest that her pancreas is working overtime to keep up with demand. This alone should warrant further BGL testing (i.e. random, fasting, postprandial, during the night). If her pancreas is working overtime so much, diabetes will eventually be guaranteed.
I might ask what she so voraciously eats? High carb foods can create that kind of vicious circle, especially when malfunctioning metabolisms are involved. She's got to get the weight down and it starts with what goes in her mouth. If her thyroid is off, this will also be a contributing factor to the weight.
Good luck and keep us posted.