Bodycam: How police could handle situation like this-Justified?

Let me add some clarity. Of course, you're right that her behaviour in general was police business; they busted her driving when she shouldn't have been, and her boyfriend had a weapon (illegally, I'm guessing) and ran. Fine.

Specifically though, I was talking about the officer's inappropriate behaviour in response to her behaviour. What he was responding to was mostly childish wailing and nothing more. That is not his business - if she needs a babysitter, that's not his job. His job is keeping people safe, and she posed no threat once cuffed and surrounded by police.

Her BF just ran and dropped a loaded weapon.

... and that has nothing to do with her, nor should she be treated as though it did, unless officers had any reason to believe that the weapon was hers.

They cuff her and leave her there screaming?

Sure. Or put her in a cruiser where her noise won't bother them. I honestly don't know why they didn't just ignore her or put her away if she was going to be so verbally annoying.

Police are not there to be kind and supportive when making an arrest.

That's ... nowhere in anything I wrote.

She was not hit, she was not abused, she was not threatened.

Actually, she was threatened.

He spoke sternly and used profanity when she was screaming profanity at him and trying to make a scene to give the appearance they were abusing her.

Sure. So? The officers are all wearing body cams, and the cruisers have cameras as well. If any of the public actually bought into her nonsense (which I think is doubtful), there's plenty of evidence to the contrary. That said, officers should conduct themselves with professionalism and that means, among other things, not engaging in back-and-forth swearing and inappropriate use (read: abuse) of authority. You don't have to agree, but it looks unprofessional, and it's frankly juvenile. Look at how she's controlling him with nothing more than her childish behaviour. He should be well beyond being controlled like that by a 17-year old.

Unfortunately we don't know if it was a one-off or if he's always like that.