You would be right if he asked her to exit the vehicle immediately. He didn't. Him asking her to step out of the car had nothing to do with the traffic stop. It was for nothing more than being in a bad mood, and not putting out a cigarette. Neither of which is against the law.
...none of which is "escalation." What escalated the situation was her refusal with his order, her physical resistant and his waving a stun gun in her face. Those are actions which took the situation and escalated it. A legal order to step out of your vehicle doesn't escalate anything.