Oh dear! You sound very caring and so does your DGD!
Please share with her that I didn’t have my last 3 (of 4) child til I got married in my late 30’s, then produced two daughters and a son at 39, 42 & 44. She has so much much time.
Maybe get her to go on some solo (not necessarily singles) holidays and join some social or community clubs. I’m sure she’ll meet someone and one day will make a fabulous mum.
Failing this, she could have a baby alone, or foster??
Whatever happens she’s very lucky to have a grandmother who clearly loves and cares about her very much 😊