How does Mona get killed?

Well in the book, Mona is a, but ik that in the tv show, they don't hav Mona as a, I'm pretty sure... But in the book, Hannah loses her memory when she gets hit, so she never got the chance to tell the girls who a was, but she finally remembers and tells the girls it's Mona but Spencer wasn't with them when she remembered Spencer was in the car with Mona so the girls txt Spencer and while in the car Spencer tries to call the cops and Mona catches her so she pulls over and offers Spencer a deal. She sed that if Spencer keeps it to herself, then se will make her popular, but Spencer declines and the fight and Mona tries to push Spencer off the cliff and the both fall and Spencer lands on grass but Mona lands on a rock and ends up breaking her neck. But I'm pretty sure the tv series isn't really following the book that much.. Hope that helped!!