Anzu used to be an alien (they never named the aliens' race in the manga or Japanese version of the anime, did they?) before she got blasted with the Mew gun during a fight against the Mews.

What happened was (this just played itself out in my mind), the aliens were fighting against the Mews, and when Pai used his giant whacky fan thing to attack the Mews, Ryou was caught up in the blast and crashed through the wall of the Cafe (yup, it was a pretty big blast), landing up against the Mew gun and knocking the 'on' switch. The beam shot out and Anzu, fighting Mint, managed to get in the way when she stepped back as Mint made a swing at her.

Wuaaaah. That sounded more like one of my stories... I might extend that later...

Oh yeah, and her alien weapon is a staff that creates a massive blast when slammed down hard (it'd be certain death if she dropped it XD).