Gardevoir Weight Gain

So you decided to choose Wendy and her Gardevoir companion? Okay then.

Wendy has brown hair tied into a pony tail and has pale skin. She wears a blue turtleneck, a standard backpack, a white jacket with black stripes running down the sleeves and lastly black shorts that matches her black shoes.

A young Pokemon trainer traveling through the Hoenn region, what will they encounter that makes her Gardevoir and, maybe her as well, to gain weight and change?