Alexa King appears in The Bone that Blew.
Her nanny (or "manny") was Calvin Warren. A very privileged, well-educated and spoiled young girl. She tried to get Calvin to do her homework for her, he refused and said he was going to tell the school.
She asked him to tell her parents instead, but he refused again since they never punish her and are unlikely to teach her consequences. Due to her school's honor policy of no second chances, she knew she'd be expelled. So she got one of her father's shotguns and shot Cal, killing him. Her mother came home and helped her dispose of the body by burning it in gasoline siphoned from the car.
Later on she and her brother spoke mandarin to insult Special Agent Seeley Booth when he questioned them and then later she appeared at her brother's lacrosse game to cheer him on.
Her mother attempted to take the blame for Calvin's murder, but Alexa was caught due to her phone messages. This was the first time her father, Richard King, heard of this and was appalled at the revelation. Booth stated that Alexa would suffer the consequences for her actions, but her mother would suffer much more. Alexa seemed unfazed and somewhat smug about this.