Princess Kate is the ruler of an alternate version of Pocketville. In her timeline, when Zull broke the Friendship Heart in two halves, instead of being teleported to the Big City, the alternate Ava was killed in the explosion. After the alternate Kate was transported to the kingdom, her clothes transformed into a royal princess gown and she became the new princess of the alternate Pocketville. Kate, Kristijan and the others somehow meet her when they travel to the alternate universe by accident and also aim up in the alternate Pocketville. Once landing and beaming down, they see the alternate Kate, who states her initial designation as the new ruler of the alternate Pocket Kingdom. They also meet the alternate version of Kristijan, who happens to be one of her Royal Guards somehow.
Also, like the prime Kate, she uses the other half of the Friendship Heart to send puppies to Earth, but initially, she also differs from prime Kate because she is the new ruler in the alternate universe.