Isabelle Lightwood
Isabelle "Izzy" Sophia Lightwood is a Shadowhunter and lives in the New York Institute. She is rebellious and very beautiful. Her cooking is often made fun of by Jace and Alec. She is known to be dangerous and often carries weapons in her tall boots.
Her signature weapon is a whip with which she is quite skilled. She dresses well, as shown when she gave Clary to wear clothes that she picked for Magnus's party. Despite this seemingly shallow and girlish side of her personality, she is shown to take responsibility for situations, shouldering the blame for her brother Max's death, despite having being struck unconscious at the time. She is comforted by Simon, and ends up sleeping (in a literal, non-sexual sense) with him. She begins to casually date Simon—who is also dating Maia at the same time—and then later upon finding out about Maia, breaks up with him. After this and seeing how she is genuinely hurt by it, begins to slowly realize that she may actually be in love with Simon, but refuses to admit it.
Isabelle obviously cares for Jace and Alec, and is fiercely protective of both of them. Because of this, she is constantly torn over the fact that her brother is struggling with his sexuality and when Jace is heartbroken over Clary during whatever problem he has with her. In City of Glass, she yells at Clary for only thinking of herself and not realizing how much pain Jace is in due to how much he really loves her.
Read more about this topic: List Of The Mortal Instruments Characters