In New York City, Clary Fray, a seemingly ordinary teenager, learns that she is descended from a line of Shadowhunters — half-angel warriors who protect humanity from evil forces. After her mother disappears, Clary joins forces with a group of Shadowhunters and enters Downworld, an alternate realm filled with demons, vampires, and a host of other creatures. Clary and her companions must find and protect an ancient cup that holds the key to her mother's future.
Multiple times; mother is choked during first fight scene, protag is choked when confronting guy about his crush, then again during fight with a witch/demon in the last third of the movie.
[SPOILER] at the end of the movie it is revealed that two main characters who are in a relationship are siblings (he’s supposed to be her brother who “died” as a baby). However in the sequels it’s revealed that they aren’t actually siblings.