Willow Rosenberg is another character from the show Buffy the Vampire Slayer. She is the same actress from How I Met your Mother. She was one of Buffy’s nerdy friends, and was in love with Xander for a long time. She eventually gave up on him and started dating a werewolf. She also became a witch after she managed to bring Buffy’s dead vampire-boyfriend back to life.
Willow was also very smart and was the only one in her group of friends who did well in school. Despite her intelligence, she and Buffy went to the same college after high school and were roommates.
At first, Willow used her witch-powers for good, but eventually she used her powers for evil. At one point in the show, a man killed Willow’s girlfriend, so Willow skinned him alive! After some magical rehabilitation, Willow was allowed to join society again when she used magic to fight demons and vampires with her friends.