Hemiarthroplasty of right hip. 70 year.

My 70 year old mother slipped in bath room on 6th March. She underwent right leg uncemented unipolar hip hemiarthroplasty on 8th. On 10th the doctor made her walk with walker support. The same day, while her diaper was being changed she experienced immense pain in the thigh bone. It turned out a fracture in femur which was not there till the surgery. Now she has been advised bed rest for 10 days. Is it possible that in the future too she may experience bone cracks if the femur is not able to take load of the replaced ball and stem? Are there chances that the replacement is not done properly? Unlike in hip replacement where it is advisable to exercise actively, due to the new fracture she had to take rest. We are worried of the future complications due to this contrasting situation.