Elaine is the female protagonist from Let's Go Pikachu and Eevee.
Game canon
In Let's Go Pikachu and Eevee, an alternate universe, if chosen as the protagonist, she sets off on her journey with her rival
Trace. On it, she takes on Gym Leaders, takes down Team Rocket, and ends up becoming the Indigo League champion. Also, she is taken under the wing of
Blue Oak, who mentors her.
Pokemon Evolutions
Elaine is a trainer trying to complete the Pokédex, and manages to be the first between her,
Trace and
Green to catch Mewtwo, the last Pokémon in the Pokédex. Unaware that they all were completing the Pokédex, Green challenges Elaine to a battle for Mewtwo but loses. It's later revealed to them that they were all tasked the Pokédex at the same time.