Melissa is a minor character from the Indigo Plateau Conference who showed up in "The Fourth Round Rumble" (Episode 79). She faced off against Gary in the fourth round and proved to be a genuinely skilled trainer—her Golem managed to beat Gary's Nidoking in what came down to a one-on-one matchup, effectively knocking Gary out of the tournament. That was pretty much it for her appearance-wise; she doesn't show up again after that battle.
Worth noting: Melissa's character was originally written as male in the Japanese version but became female in the English dub.
Content compiled by AnimeList.moe from publicly available sources.
