To your points...
1. It was a valid stop for a valid traffic violation. Cops stop cars for that all the time because it is the law. Many accidents occur because people fail to signal.
2. Nobody ever said she was under the influence, but her history suggests drug possession
3. He didn’t ask ‘if’ she was irritated, but rather ‘why’ she was hostile. This was a valid question to understand her hostile behavior, which started from the beginning of the stop.
4. Both should have been more respectful and polite
5. In TX, asking her to put out the cig or get out the car are both appropriate. We don’t know the cop’s motivation yet, but he may have had a valid reason. He may not have. Either way, her refusals gave him a valid reason since her refusals were in violation of the law. She was still detained.
6. The physical altercation could be out of camera deliberately (we don’t know yet), but it could also be because she was fighting and resisting him. People that do that generally don’t stay in one place. They will pull away from the cop, forcing the cop to give chase. The cameras don’t move so if the suspect moves, the cop has little choice, but to move also. We don’t know the details yet
7. The cop was rude, which may be against policy, but not illegal. Her refusals were illegal, which led to her arrest so the fault lies with her.
She was in jail for 3 days. She threatened to call her lawyer on the video, why didn’t she call him and get out of jail? Spending 3 days in jail for a minor traffic infraction seems a bit much.