Sabrina (サブリナ, Saburina) is the Gym Leader of Saffron City's Gym, known officially as the Saffron Gym. She hands out the Marsh Badge to Trainers who defeat her. She is a young lady with psychic abilities, and thus trains Psychic-type Pokémon.
Sabrina inherited her psychic power from her father, who had the ability to teleport from location to location, as well as telekinesis. It manifested when she was young, and it was soon apparent that Sabrina's abilities far exceeded her father's. She was able to use her psychic powers to do many things- teleportation, telepathy, psychokinesis, and transmutation.
As her power increased, she grew more obsessed with developing it. She became less and less emotional, using her abilities for destructive purposes, even transforming her mother into a doll. This caused a deep psychological rift. The emotions she tried to shut off developed a separate personality and was set into a body of a relative- her own younger brother, Sean, who acts as a puppet around Sabrina. Sabrina's mind was divided into two inside two bodies: Sabrina, the cold, callous woman with a thirst for power and Sean, the little kid who just wanted to have fun.