I've heard she was in Platinum in the battle frontier, so anyone have an idea why they reused her?
In HeartGold, SoulSilver, and Platinum, Caitlin is the employer of Castle Valet Darach and oversees his Battle Castle battles. She is responsible for determining how many CP the player should receive depending on the outcome of the battle. She is said to be the most important person in the Battle Castle and acts like its princess. In Black and White, Caitlin appears as a member of the Elite Four of Unova; she traveled to the region alone in order to develop her skills further. It is revealed that she possesses some sort of psychic powers, and that in the past, she had an explosive temper that would erupt if she lost a battle causing her psychic powers to cause a lot of damage. This may be the reason why Darach fought in her place in Generation IV. It may also explain why she is quite impatient, as she demands that Darach give the player Castle Points "at once!" after each victory in the Battle Castle.
Though I think she was popular in it so they brang her back as a Elite 4 member. This is all I could find on her anime dayview.