The vehicle was still running, that's why the cop tased her. Reaching into a running vehicle is dangerous, even if it's in park. Even with a cigarette between their fingers, you'd be surprised how fast someone can shift into drive and pull a cop halfway down the road. You know what they book you for then, right? Attempted murder.
Edit: By the way, don't listen to all of that moaning and screaming. That's all a big show, it's all for the lawsuit. She received two 5-second shocks. The police officers have all been tased before, they know how it feels. Once it's over, that's it. No pain, no aftereffects at all. Motor control returns to normal. All her acting is just annoying. The extent of her injuries was some bleeding from her arm where she ripped the probe out herself. The process of removing the probes is painless and does not usually draw blood.