Answer:
The finding is expected. This is due to older people having a very depleted amount of proteins and calcium which affects their bone density.
Aged people have a large amount of osteoclasts which is responsible for the the breakdown of bone for repairs and remodification which poses a great risk for decreased and weakened bones.
The 9 yr old grand daughter however has large amounts of osteoblasts which help in bone production and translates to stronger bones.
This features and findings are the assumed and likely reasons why the 75yr old woman had fractures and the 9 yr old grand daughter suffered none.