Stephanie

In Having a Wailord of a Time, Stephanie was going to select her first Pokémon from Nurse Joy in Slateport City. However, while Ash, Brock and Max were guarding the starters, the Torchic became impatient, and began running around the Pokémon Center. Eventually, all the excitement caused Torchic to evolve into a Combusken.

Initially, Ash and the others were going to hide the Combusken and use May's Torchic as a diversion so it would seem like nothing would happen. But, fearing Stephanie would choose Torchic, they confessed to Nurse Joy what had happened.

Nurse Joy told Stephanie that Combusken would probably be a bad Pokémon for a beginning trainer to use, so she chose Mudkip. Then Stephanie's father looked into the Treecko's eyes and fell in love with it. Nurse Joy allowed Stephanie's father to bring the Treecko with him, and she decided to keep the Combusken with her at the Pokémon center.

In the Japanese version, she was never given a name. She was only referred to as "Girl" in the credits.
Her English name, therefore, likely was inspired by her voice actress' name.

(Source: Bulbapedia)