OP, YABU to judge on her behalf.
YANBU if you choose NOT to embark on a pregnancy when you are 50
.
It would not/will not be my choice, but then again I had 4 boys between 37 and 44 and that is quite enough, thank you very much.
Biology is a bit of a non-argument IMO, for many reasons. There are so many ways in which we manipulate what nature 'intended' (for the record, natrue does not intend anything, but via evolution we veeeery, very slowly devolped the way we did), so why not in this way? And yes, a 50 year old father would not face this amount of scrutiny over his choice to father a child at his age.
There is a theory, that biologically speaking human females should have their babies in their late teens, fathered by an 'older' male @25-30 who would be an experienced hunter and by virtue of still being alive had proven that his gene were good material. Next 15 years are spend with child-rearing, then by the time she's 30 she is a Wise Woman and may take much younger man as a toy boy to teach him the way of the world ie sex
.
That scenario is so NOT what my live panned out like!!