Medley is described as an avid partygoer and performer who loves attention, sometimes going to the extreme with loud music and everything else you'd expect from a party dialed up to 11. This behavior is almost certainly proven to be true in her dialogue before fighting her, as she is very flirtatious with Kai, calling him a fan and "handsome", and calling him a killjoy and saying that he has no spark of joy when he tells her about her speakers needing to go.  

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Have some fun with this one - while I don't want sporadic energy, I'd imagine Medley sounds like a toned down Iono from Pokemon Horizons, or maybe the opposite side of the spectrum like Rouge from Sonic to set a reference.

Medley's Dialogue