It’s not the butter, it’s the sugar and grains. Caveat: the butter needs to come from clean, healthy animals.
If she gives up all sugar and starchy carbs, especially wheat, max 1 fresh fruit serving a day, her diabetes would be gone in a short time. She can eat plenty of healthy fats.
True, but healthy fats come from nuts, avacados, olives, coconuts, and seeds, not animal and dairy sources.