I understand that she was not the daughter of one of the favored wives - so she might have been "trying harder", as it were. If the Greeks were following Egyptian custom, the first born daughter would have been the one selected as "Throne Daughter" - i.e. whichever of her brothers was selected as heir would have been married off to her to make it clear who the next ruler would be.
According to the late Barbara Mertz this is an inaccurate idea. One of the reasons they say this? There was no title for that. Later dynasties did have a title - but that was a title for a ritual priestess which was a hereditary position.
I'm prepared to believe that an article written an unknown number of years ago but read in college (we'll average that out as about 35 years ago) was not the most up to date with CURRENT Egyptology!
It may also have been a simplification for narrative purposes, as I think that they were explaining why one of the pharaohs who LITERALLY took the throne (no heir of the previous pharaoh survived some war) married one of Pharaoh's surviving sisters (or wives - it's been 35 years) and then married his own oldest daughter as a ritual way to cement his own "legitimacy" as pharaoh. Because to many non-Egyptians, the marrying your own daughter thing was...well, icky. The writer did state that the daughter never conceived and it might be that marriage was "in name only" for ritual purposes.
After three to five thousand or so years and I don't know how many dynasties later, even while pharaohs ruled Egypt, I don't think that it made much of a difference either way.
But there were signs of serious inbreeding in the Egyptian royal dynasties, at times - the heretic king, Ankhnaten (sp?) had several noticeable oddities - and was one of the few who had "natural" portraits made, instead of "perfected" ritual portraits made, which was the custom for thousands of years (something Egyptologists of 35 years ago and today generally agree on - there were brief periods when "natural" or "realistic" schools of art came into fashion but they didn't always last).