Sabrina is the 6th gym leader in the original pokemon games, in which she specializes in psychic-type pokemon. Sabrina is certainly not easy to battle, as her team is pretty strong. Her Alakazam took out a good few members of my pokemon during my battle. You can face her again in the 2nd generation, but by the time you reach her it's a piece of cake.
Her fight against Ash in the anime is what I remember most. She is first an unstoppable and somewhat crazy gym leader. But it all works out in the end.