https://wikirby.com/wiki/Adeleine#cite_note-2
>Welcome Adeleine & Ribbon back from "Kirby 64"! Sorry, up until now we went on a trip a bit far-off... but, my paintings have gotten even better, and I've come back with Ribbon. So, let us join, too!

Did Adeleine suddenly disappear to further her art studies? She was originally on Popstar to do that, but the way she feels sorry about it sounds like she's come to think of Dream Land as her home.