Daphne returned to Hogwarts mainly to get anything she needed and to inform Luna of the trip. Apparently Luna was extremely ecstatic, nearly jumping off the walls, yet she also seemed to know it was going to happen. She might have known through her gift that it would happen, but not when. She seemed to have been prepped for it for some time and was practically ready to leave the school. After a short conversation with the Headmistress, both of them were allowed to depart for extended leave. Hopefully it won't be permanent.