I’m 64 and male and I’m not sure I could have ever sat like that.
She’s 50. Maybe it’s a yoga thing. I just can’t imagine how that position could possibly be comfortable. You can do it. Just because you can, would you ever want to?
I was a gymnast (almost 50 years ago, lol)...I do pilates (hate yoga) and have always been active. Now, I wouldn’t sit there a long time, but it’s useful and sometimes comfortable.
I’m 67, male, and I can still sit like that; just not as long as I used to.
If your just 64 and can’t sit like that, I would advise you get up and move a lot more.
If your a vet, try some of the old rifle range snapping in positions.
If you cant get into them, you need to do a lot more physical labor.
Just a suggestion.