A police officers doesn't require whatever your definition of "need" is to ask someone they've pulled over to leave their car. You get pulled over for a traffic violation and get asked to leave your vehicle, you leave your vehicle. That's the law.
She escalated the situation and forced him to us force to get her to leave the vehicle. Does that mean she should be dead now? Of course not, but there's no need to make up tales about how she only found herself in this mess because of a power tripping cop.
The cop has to state the reason of arrest if asked. She asked and he ignored her.