To celebrate St David, everyone in Wales wears a Welsh symbol on their lapel, either the daffodil or the leek.
Welsh cakes, a cross between a scone and pikelets, are given out.
On Wednesday, Sophie celebrated a day early because she was off to her pre-school Smart Start, which she does not attend on Thursday.
She wanted to celebrate with her friends so they all made Welsh cakes, and sang Welsh nursery rhymes.
In the afternoon, still dressed in her Welsh costume, she delivered Welsh cakes to her grandmother and later to her father, a teacher, and boys at Wanganui Collegiate School.
Mrs Banks said before they left Wales two years ago, they had promised Sophie's godparents Sophie would always honour St David's Day.