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DJ Buena.
Never shown on any artwork, card, anime or manga. Nothing of her exists at all (there's slim chance that she appears on one of the pages of the HGSS Quiz Encyclopedia that haven't been scanned by PacificPikachu [PokeScans] or in the lost Emiko Yoshino's Crystal manga, but both are doubtful).
This is probably the only fanart of her in existence. Purely imaginative, drawn by some Japanese Twitter artist (don't recall the name, sadly), drawn as part of the series of arts commemorating the 20th Anniversary of Crystal's release, the arts depicted its novel aspects.
Can you get more obscure?