I think this sort of "I'm one up" female competition is not unusual.
Go to any hospital and see how some females just love to (mis)treat nurses as being one down on them.
It is nothing but compensation for an inferiority complex IMHO.
Imagine this aunt be going on like this in front of a GG that for some or other reason never could have children, but may have loved to have some!?
That is so very thoughtless and unfeeling. Just so to enjoy the notion to be one-up --- yet it's not too uncommon.
In olden days females would "take on" the titles of their husbands (they'd earned) and so become Frau Doktor, Frau Professor, or Frau Geheimrat... and walk about like peacocks, treating the rest of females like trash.
One hopes to have out grown this kind of behaviour with female emancipation, but your aunt obviously does not feel emancipated. So she has to use her fertile womb to bring other females down.
That's very childish and cruel.
Axelle