Diabetic folks

understand type 1 is insulin dependent, your body does not produce it. type 2 could be either depending on it's progression.

I think first and foremost is getting her to accept it. There are cases of insulin dependent now on oral, and oral not taking anything and maintaining. I am unsure of the statistic's and their circumstances though. As far as I know there is no cure.
I think getting started with some of the suggestions here prior to a nutritionist, I especially think her keeping a food and testing log for a month will tell her which foods currently in her chain cause her to spike. It is different with people. Things that effect others might have little to no effect on her. So that's why the log and testing in regular intervals, at least at first, are key.
That info can help a nutritionist develop a plan for her to make a change w/o just flat blanket cutting foods she enjoys creating even more resistance to acceptance.
Yes diabetes has no real cure, but it also doesn't need to define who you are. I can now eat nearly any food I wish to but I also know how that food will effect my BGL's. A food spike isn't going to kill you it is the consistent elevation that will cause internal organs to fail among other things. It sounds like there are some simple things she can do now to protect herself and get this in HER control.

Was she recently diagnosed and has she been seeing a doctor regularly for check up's? If it just came to light and hasn't been a progression of years than even better.

I feel my best at 120-130 when I get around 100 I start feeling weak and confused, around 60-70 I am ready to pass out. Around 170+ I feel flush like my face is on fire it is a burning sensation like a sunburn. I keep glucose pills around for when I get low.