It's time for a reality check.
Those who are encouraging Nurse Getty to pursue this "dream" either do not have a clue about the real demands of nursing or do not have a clue about the realities of being 70 years old.
Similar to Nurse Getty, I was a petroleum geologist in my first career. In my late 30's I went back to school and became an RN. Since my wife was an RN, I thought I had a pretty good idea about what I was getting into. In reality, I didn't have a clue. A career in nursing was much more demanding than I could have imagined. It is physically, mentally, and emotionally demanding. On most days you will leave work physically exhausted and emotionally drained. I retired from nursing at 62 and I'm currently 66
Nurse Getty and I are both senior citizens. No matter how hard we try to convince ourselves that we are "youthful", we are still old. I put in 4 miles, almost every day, so I am in fairly good shape for someone my age. Still, I would not consider returning to work because of the physical demands of nursing. The OP is correct. Most nurses are younger and there is a reason for this.
Also, whether Nurse Getty and I like to admit it, as we approach 70, we are not quite as sharp as we were compared to 5 or 10 years ago. In the petroleum industry a mistake might result in a dry hole. In nursing, a mistake can literally kill someone.
I suggest that anyone considering a career in nursing should first become a CNA. This can be done within a few weeks. Working as a CNA for a period of time will give you a feel for whether working in healthcare is for you.