You can look up her lore as Kasane Teto, she started as an April fools joke in 2008 but became popular through the UTAU userbase as a vocaloid 'parody' even when she sounded just as good as Miku in the hands of the right producers. She's been given official status fairly recently (2023) as a voicebank that can be purchased and used with the top paid competitor to the Vocaloid software, SynthesizerV Studio. You can find live performances of her and Miku on stage together, which has further fueled her official status as part of the vocaloid lore. If I keep going this will end up a book so I'll leave it there lol.