Isabelle (Izzy) Lightwood is the only female child of the Lightwood family. She is the middle sibling of Alec and Max.
Isabelle is described as beautiful often, with black hair and dark eyes. She is also very tall, and because Clary is small and delicate, she is often jealous. She is the opposite of her brother, always running head-first into situations and often dates Downworlders. She is very close with her brother Alec, being one of the only people to know of his sexual orientation. She often throws tantrums and locks herself in her room. She is very fashion-consious and helps Clary with fashion and make-up advice.
Isabelle is played by Jemima West in the movie
Izzy first uses her beauty to lure a demon away to trap him and have Jace kill him. This is where she first sees Clary. Her special weapon is an electrum whip which she uses and takes with her wherever she goes. Isabelle, like everyone else, is shocked that Clary could kill a demon and is infact not a mundane. In City of Bones, she also meets Simon, Clary’s best friend, who takes a liking to her. Despite Izzy trying to make her feeling for him unknown, when Simon is transformed into a rat she seems to panic a little, making her feeling for him a little more obvious. Later in the series, her and Simon enter a relationship.