LilligantLewis
Bonnie stan
Mawile is half Steel-type though, so I think that the writers went with Spritzee instead because it was pure Fairy-type. Then again, idk why they didn't just make Sylveon be Valerie's ace like in the games...
The main reason they went with Spritzee is because Ash hadn't dexed it yet. Its only prior appearance (not counting background) was when he fell off the plane with Alexa and saw two Spritzee as his first Kalos region Pokémon, before he had his dex