I was diagnosed with T2 diabetes over 30 years ago. I was told it would inevitably get worse over time and I'd end up taking insulin.
Well, here I am 30 years later and I don't take insulin and my condition hasn't got worse, so I guess I must have been doing something right.
My advice would be to cut the carbs - and not just obviously sugary foods. If she's not veggie, eat meat, fish and veg which grow above ground, restrict fruit, cut out cereals and flour. Eat mainly whole foods.
If your daughter has been diagnosed, she'll probably be sent on a course and have her BP, cholesterol and weight checked. If she's overweight, she'd benefit from gradual weight reduction. She needs to exercise, but it doesn't need to be anything too drastic - just keep moving and do whatever she feels comfortable with. Resist any "quick fix" remedies because she needs to get used to the fact that changes are for life, so she needs to do things she'll stick with.