Now retirement age is 67, anything under 5-8 years of being retired seems to be a real short change to me so I would say under 75 is too young .
However in reality sometimes people are quite unwell in their 60s and 70s so dying in 70s isn't a surprise when fighting serious ill health. It's very hard when someone is in rude good health and suddenly dies even when they have been really independent until the last year.
In terms of dying from an accident or terrible disease earlier- any child dying, 20 or 30 year olds is absolutely tragic as is the death of parents in their 40s and 50s.
So in summary she 75 or above. The average age of death is 86 for women and 84 for men I think. If you die in your 80s it may be too young for rest of your family but you've had a good innings and lots of memories of important life events you've been able to be part of 🥰