My mother was diagnosed at age 18 with Type 1 diabetes, and died a few years ago at age 59 from the effects of the disease. By the end, her entire metabolism was way out of whack, her sugar nearly uncontrollable, her digestion dysfunctional, and she was suffering from hypertension.
The good news for you is 1) Mom still had her feet and toes, 2) Mom could still see as well as ever (she was awfully nearsighted from youth), and 3) Mom was a drinker and smoker who didn't eat right, didn't control her weight, and didn't exercise.
Your daughter ought to be able to do far better than my mother did, if she even gives it half an attempt.
I think the most hopeful thing is that testing and insulin technology is so much better than even a few years ago, and can only get better. It seems to be nowhere near the threat to day-to-day life it was in the days of pork insulin and urine tests.