Ride your own ride, drive your own car. There are countless reasons, some good and some bad, why other drivers handle their vehicles differently.
The only video I have seen is the one from the car. Maybe Mr. Aggressive tailgated her and then whipped in front of the truck before she could make the lane change herself.
Her story, I believe, was she pulled into the right lane after completing the pass to let the aggressor go, but then she must have pulled back into the left lane. Maybe that was his breaking point; maybe she flashed her high beams or honked her horn; maybe she decided to try and tailgate him or.... all that said, people die when stopped on the highway, and even though thinning the heard of such dead weight may be ideal, my morality gets in the way. No justification for the stoppers actions.