I will be 65 next month and I did a double knee replacement about 4 years ago. I wish I had done it earlier but the doctors said I was too young (?????) It was the best thing I have ever done. There were days before the surgery that I could barely walk. I had gone through several sets of the injections in the knee but they gave minimal relief.
I was given the option of having them done one at a time or both at the same time. I decided I didn't want to go through it twice.
I bought a book from Amazon written by a doctor and a physical therapist who had been though the surgery so they had great perspective and told exactly what to expect. One of the best things I did was to exercise the leg muscles a lot before surgery so the muscles were in good shape before the surgery so that when they were cut it did not take as long to heal. I got this from the book.
It was painful but the results were wonderful!!! I seldom have any knee or leg pain and if I would take off a few pounds I probably would not have that.
I would not think that she would be able to do the sports that she has enjoyed in the past but she would be able to enjoy her life.