Riding my bike in traffic, I sometimes see car drivers do things so dangerous that it brings my blood to a boil, and I chase them down and yell at them. Looking back on it later, I've wondered why I lost my cool. Not that I get violent; but emotion definitely overpowers self-control. In light of this... and I didn't see it the first time I watched the video... but the girl who got her ponytail yanked had a whole fistful of the other girl's shorts in her hand at the time. As I sometimes have to say to my kids... "well, what did you think was going to happen, if you did that?"
Also, if you watch the clips in sequence, the clip preceding the ponytail pulling episode shows the BYU player flipping #15 on the ground. But again, she went a bit too far in her retaliation. Maybe a yank on the ponytail, but not a throwdown. Gotta be a little more subtle.