|“||You're my little brother, you dumb idiot. I love you no matter what.||”|
Rebecca Lewis is Simon's older sister.
Rebecca was born a few years before Simon and is quite close to him. Having shown an affinity for drawing since she was young, Rebecca eventually went on to become an art history major in New Jersey. She still occasionally returned to their home in New York to visit her family during holidays, as well as to do her laundry.
Once, when she returned to New York to find their house full of Jewish symbols. She tried calling Simon, who was avoiding her, not wanting to get her involved in the Shadow World. Later, Simon ultimately agreed to meet with her, and Simon, in an effort to help her understand what was happening to their mother, finally revealed to her that he was a vampire. Despite the revelation, Rebecca still accepted her brother. However, her memories of what transpired between Simon and her mother, of what Simon told her, as well as memories of Clary, were removed from her mind when Simon was made mortal again by Asmodeus merely weeks after finding out.
When Simon went to the Shadowhunter Academy to train for Ascension, she and Elaine—both still lacking of their memories—were led to believe that Simon was going to a military academy on a scholarship. When Simon returned years later to bid them farewell just before his Ascension, knowing he would be barred from making contact with them again once he becomes a full-fledged Shadowhunter, Rebecca had been asleep and Simon decided not to wake her, opting instead to leave a note for her and their mother.
Since his Ascension, Simon managed to find a way to communicate with Rebecca: collaborating on an "epic, exquisite-corpse style manuscript," alternating sentences through text message. The hard-to-follow story involves space travel, warring kingdoms, and multiple types of aliens.
Years after, Rebecca began working at a restaurant in Brooklyn. Simon and Clary found a way to tell Rebecca bits of his new life—about being Shadowhunters, the existence of the Shadow World, and the general idea of what Simon went through since becoming a part of it. She also may have regained bits of her memory, having remembered her mother's comment about Clary when she and Simon first became friends. In 2012, Clary hired her to provide catering for and attended Simon and Isabelle Lightwood's sudden engagement party. She brought a prepared video containing pictures of Simon from his childhood, as was mundane custom.
Rebecca is shown to be a very good elder sister. Understanding and supportive, Rebecca accepted Simon when he told her that he was a vampire. Also, when their father died, Rebecca took up the mother's role in the family since her mother was "a lying zombie." Overall, she is a caring sister, reading stories to Simon when he was a child, and packing their lunch when their mother couldn't.
She was also said to have quite a drawing talent. She constantly took up classes on art and eventually went to college in New Jersey.
She has dark brown hair, brown eyes and freckles across her nose. Her eye shape resembles Simon's. Her favorite dress style is vintage and it is said that she also sews some of her clothes herself.