The legality of what she does at the end (BIG SPOILER)
THIS HAS A BIG SPOILER!
At the end, she did not have to run him over to get away. She could have just drove away, as her brother said. Obviously she did what she did because he killed her parents but legally she would be guilty of murder. The movie gives people the impression we can get away with killing someone if we have decided it is justified or if we think they might kill us some time in the future.
California, and as far as I know most states, have the concept of imminent threat. The threat must be real and unavoidable without the use of deadly force. In other words, if you can get away from the actual threat at that moment then you cannot legally use deadly force.
I am not an attorney but the law must be understandable conceptually by everyone so don't say I must be an attorney to know what it says.
Many people don't understand about the requirement for an imminent threat and when the use of deadly force is legal and this movie perpetuates that misunderstanding.