"I think it's wonderful news," she said as the couple met crowds during the second day of their visit to Yorkshire.
"I think mother, son, father are all doing well and I think it's a wonderfully uplifting moment for the country.
"It's very exciting and it's wonderful for the grandfather," she added, pointing in the direction of Prince Charles.
"He's brilliant with children, so he'll have a wonderful time."
The couple are in Yorkshire on an official visit and are due to visit Burton Fleming and meet members of the community affected by the floods in January 2013.
They are also due to visit a fish and chip shop. The award-winning eating establishment, owned by Suzanne Gilbertson and John Hutchinson in Bridlington, is busy preparing for the royal visit.
"We're all very excited about it but it's taken a little while to sink in," said Suzanne.
"Apparently, they'll be here for 15 minutes and we've been told they're fantastic at chit-chat so we don't have to worry about what we'll say to them.
"I'll offer them a Golden Years portion. It's what we giver the older generation at lunchtime. It's also called 'fish and a penneth (penny worth) of chips."
After being informed by his son William of the happy news, Prince Charles released a statement saying he was "enormously proud and happy" about the birth of his grandson, the future King of England.
"Both my wife and I are overjoyed at the arrival of my first grandchild," a statement from the Prince of Wales read. "It is an incredibly special moment for William and Catherine and we are so thrilled for them on the birth of their baby boy.
"Grandparenthood is a unique moment in anyone's life, as countless kind people have told me in recent months, so I am enormously proud and happy to be a grandfather for the first time and we are eagerly looking forward to seeing the baby in the near future."