There's no doubt that she needed to be physically controlled and arrested--8 minutes in a situation where both were at risk due to her erratic behavior is about 7 minutes too long.
I wonder what the cop trainers will say when using this in class. It would seem to me that he had the option of grappling with her and taking her down (arm/wrist lock with a leg sweep, etc), maybe a similar move backed up with the baton, or using the tazer. One advantage of having hold of her is to prevent her from staggering into traffic. A disadvantage with wrestling her down is the increased chance of snapping one of her bones or even a hip--not a minor thing. The tazer probably put her at greater risk of cardiac arrest than other methods. Keeping his distance probably kept him safer from her and from getting pulled into traffic.
She started it, she continued it, she could have gotten reasonable at any point and things would have been fine. Watching the video is a lot different from being on the spot, and I think the cop's actions were acceptable and I hope this doesn't wind up hurting him or his department.
vicente - Unfortunately, there's no way to show the public the 98% of cases there everything goes well. It's the flashy/interesting videos that make the news, no one wants to see the "good" stuff.