Rikku had heard that there was a new girl on campus, and that she was looking for her. Which was odd, because she'd never heard of the girl before. At any rate, when she stumbled into someone and they communicated that a Kairi was looking for her, she promptly looked the girl up in the schools registry.
Perhaps word of her skills with machina was getting around and the girl had something for her to fix? Hopefully!
Ambling about the maze of the dorms, she found the designated one and rattled a tune out on the door. Then she realized there was a doorbell and chimed it several times.