Just because a police officer is "off-duty", that does not mean they are "off-duty", They may not be on the clock, but they are still sworn peace officers and as such are obligated to up hold the law. This woman was clearly in the wrong. He was clearly a police officer who did identify himself. She should not tried to flee, regardless of how she felt about the situation.

When I was a kid, I was taught that the proper response to a police officer was: Yes Sir, No Sir, Sorry Sir. The take-down was in line with policy and not brutal.