Amanda was a teenage girl and serial killer who acted as the main antagonist of The Sleepover Massacre.
Amanda was the daughter of Tiffany, older sister of Tamara and younger sister of Matt. They all lived together in the same house. Amanda's father died in a car crash thought to be an accident, but is was later revealed that Matt and Tiffany had conspired to kill him.
Amanda showed early signs of being a possible pyschopath, so the concerned school principal told Tiffany to take her to see Dr Vance, a child psychologist.
One night, Amanda was unable to sleep. After masturbating, she went to the bathroom, and heard something in her mother's room. Amanda crept up to the open door and silently observed Matt and Tiffany having sex, uncovering their incestuous affair. This finally caused Amanda to snap and she set fire to the house, killing Tiffany, Matt and Tamara.
The police suspected Amanda, the only survivor, to be the perpetrator, and contacted Dr Vance. Vance took Amanda to his home office. There, he explained that he could save her from being arrested and imprisoned by not revealing the file he had on her, which confirmed that she may be an undiagnosed psychopath. However, in return, she would provide him with sexual favours. Amanda agreed and Vance lied to the police, and so Amanda got off scott free. Vance and Amanda's sexual affair lasted for an undisclosed amount of time, but she eventually grew tired of it. One night, in the middle of sex, Amanda unexpectedly drove a knife into his neck, killing him.
Some time later, Amanda revisited her old house, only to learn that Laura had moved in. Amanda noted a resemblance between Laura and her late mother, and became obsessed with her.
During Friday daytime, Amanda continued to stalk Laura as she always did. At one point, she came across the car of Josh, Laura's boyfriend. Without showing any emotion, Amanda urinated on the car when nobody was around.
On Friday night, Amanda arrived at the house and continued to watch over it, until Josh came out of the house to get beer from his car. Amanda took the opportunity to plunge a knife into his back and prop his body up agaainst the door, leaving Laura and Lynn to find it.
Then, she snuck into the garage and cut the power, before going upstairs and murdering Beth by slitting her throat.
Laura and Lynn later came upstairs while Amanda hid in the shadows. When Laura went to the bathroom, Amanda snuck into the bedroom and killed Lynn, then waited for Laura to return. She attacked her, but Laura knocked her out using a torch. Laura then hid in the closet, where she found Beth's body. Beth's body fell out of the closet, clueing Amanda in as to where Laura was hiding. She opened the closet and attacked Laura, but Laura managed to grab Amanda's knife during the struggle and gut her.