Don't have any particular detail on the Type 1 DM and cholesterol, but 1 year is probably just the start of the healing process.
My partner has Autoimmune thyroid, it took over 5 years for her thyroid to resume full function, our approach was multiprong, medication, toxins, diet, supplements, yoga, meditation, sun exposure, exercise, stress reduction etc, etc. anything that may be of benefit should be encouraged and anything that may harm should be eliminated.
So along with diet, I would suggest she look at all those other areas as well, good diet will be negated by emotional self sabotage or other negative aspects in her life.
My sister went through a difficult emotional period in her life, she ate healthy and heaps, but could not gain any weight just because of the stress.