Jacqueline, nicknamed Jack for short (Cassidy Freeman), was a villainess from "Tiny," episode 2.13 of Once Upon a Time (airdate February 10, 2013). She was a villainous female version of the titular male protagonist from noted fairy tales Jack and the Beanstalk and Jack the Giant Slayer.
In the episode, Jacqueline is introduced as the lover of Prince James, the evil twin brother of David/Prince Charming, and they were engaged in a sexual dalliance in James' bedroom when his father, King George, informed him of a giant in the kingdom. Jacqueline and James found the giant, Anton, and the former (who introduced herself under her nickname, "Jack") gave Anton a mushroom to make him human-sized. She and James played on Anton's emotions by telling him that the kingdom is destitute, leading to Anton offering to bring treasure to them to save the kingdom.
Shortly after Anton returned home via the beanstalk to gather the treasure, both he and his older brother, Arlo, discover that Jack and James climbed up the stalk as well, and they revealed their true villainous nature and their plan to steal all of the magic beans for their use. The couple brandished their swords, which were laced with poison, and killed all of the giants, leaving Anton and Arlo. Jack used her sword to kill Arlo, but before he succumbed, Arlo stabbed the villainess with the same sword. Jack reached out to James, only for her lover to run off with the stolen treasure, leaving Jack to die.