For what it's worth, the submitted fanart still up on the Japanese Kirby 64 official website also refer to her as Ado. I think it was an unfortunate combination of her redesign overseas being first seen in Kirby 64 than the KDL3 manga >>536249445 and Adeleine *probably* being the name they wanted to use in the first place but shortened on the stage select screen, and >>536251223 HAL poking fun at both literal wikifags and gaijin who couldn't let go of the idea that Ado was a boy for their fanfictions.
>>536251789
Are you thinking of the Dedede directory?