Ellen Danielle Dunkel is the female duplicate of Elliot. The process that made her in theory also made her bisexual but She describes her feelings for boys as "tacked on, like a poorly written side note". She is currently dating Nanase
Ellen first came into being in the fifth chapter of El Goonish Shive's second story arc, Sister. But the process that resulted in her started when Tedd shot Elliot with the female version 5 transformation beam (the beam adds Heterosexual attraction on gender morphs by default). When Elliot touched the Dewitchery Diamond, his "curse" of being female was 'removed' by being split off into a second person, thus creating Ellen.
Ellen first found out Nanase liked her when Susan panicked after Nanase used the fairy doll spell. Nanase was unaware of Ellen's knowledge of her feelings until the tail end of Grace's "transgender" birthday party. From there they hid their relationship in public until Nanase's mother caught them kissing after Ellen was nearly killed by a misguided wizard and Nanase had to fight said wizard using her fairy doll spell and her guardian form. They are now very open about it to the point of kissing at school.