Her hostility may have triggered a red flag. Plus he probably knew from dispatch that she had previous drug ( including MJ) and alcohol arrests. Her attitude and her history probably made the cop suspicious so he decided her ask her additional questions. He asked her to put the cigarette out so she didn’t try to burn him with it due to hostility or because he was attempting to smell drugs or alcohol. Cigarette smoke is commonly used to mask the other smells. She was already legally detained for the traffic stop.
Thanks - you seem to know a lot about this and it’s very helpful.