These heart-to-heart are SO important! I’m glad that she had a chance to vent a lot of her concerns.
For me, the biggest emotional concern about being diagnosed was how it would affect my future ability to have children… even though I wasn’t thinking about having kids THEN. But I am now!!
The chances of the children having diabetes is quite low (I think around 5%), but diabetes and pregnancy does take special care and attention! But there are so many women who have had successful pregnancies and share their stories about it. It might help your daughter to read these stories and know that EVEN without a cure, she can live a normal life and achieve her dreams 
But we are all hoping for a cure for her and many others who struggle with diabetes!
Sounds like you have a very mature daughter!!