Labeling insulin as your «fat storage hormone» not only misrepresents it's true biological activity, it scares people into believing that insulin is the enemy, and even
small amounts of insulin cause weight gain, obesity, and type 2 diabetes.
But it is also possible that the years
of stress on her pancreas not to mention the drug you said
caused some damage might have done sufficient damage that it can't produce enough
insulin on its own to overcome even
small amounts of insulin resistance
caused by
small amounts of meat, eggs or dairy and that for her only a 100 % WFPB diet will allow her to control her blood sugar without medication.