Emily is Katie Fitch's twin sister, who she is younger than by a few minutes. While they were young, they developed their own cant-style language that only they understand.
Emily is initially presented as being very quiet and a "doormat" to her sister Katie. She often be bullied and taken advantage of by her dominant sister Katie. As the show progresses, Emily begins to come out of her shell and strives for individuality. Much of this is due to her becoming okay with her sexuality and her feelings for Naomi Campbell.
Much of the third series deals with her dealing with her sexuality and coming out to her friends and family. Up until Pandora, Emily maintains that she is straight, but is convinced by Naomi to accept her sexuality. By Naomi, Emily has accepted that she is a lesbian and she and Naomi share their first sexual experience. By the end of the series, Emily comes out to her family and she and Naomi both come out publicly as a couple.
Much of the fourth series deals with Emily and Naomi having problems with their relationship, mostly due to Naomi cheating on Emily while also having contrasting plans on whether they should go to University right after graduating or not. By Everyone, their relationship is on the rocks, but Naomi finally reveals her true feelings: that she had always loved Emily and that she is done running, and presents to her two tickets to travel after graduation, and thus she and Naomi reunite.
Emily's profile on E4's official Skins website.