Dana Foster is a character from Step by Step, a fellow show on TGIF. She appeared in Disney World in The Happiest Show on Earth as a part of a crossover with Boy Meets World, as Step by Step was airing a Disney World episode at the same time.
Dana briefly speaks to Cory when he visits the Living Seas Pavilion, looking for Topanga. She explains Amber's situation when Cory showed up, and made him apologize when he said Amber was "just a fish." Before she leaves, she wishes him luck in finding what he's looking for.