"It's nice to have the gender balance restored. It has been unusual that there's been so little in the way of girls in the royal family for such a long time," she said.
"George III had lots of daughters and so did Edward VII. There has been a dearth of young princesses in the close royal family."
She added: "Quite a number of queen consorts have been tough and formidable in their own right. What is nice is that women born into the royal family make their own way.
"It's the women in the last couple of centuries who have lived longer and in a sense done more and wider things.
"I think it's a good thing Prince George has a sister. It will take some of the pressure off him when he's older."
Royal author and historian Hugo Vickers said the new baby may one day be known as the princess royal.
Customarily given by the sovereign to his or her eldest daughter, the honorary style is currently used by Princess Anne.
The birth comes as the Queen prepares to overtake her ancestor Queen Victoria as the longest reigning British monarch in history this September.
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- PAA
