You can't be serious, right?
You don't have to see someone to cut that person off. In fact, once you see them it's too late to cut them off. You feel them, you hear them, but you don't see them. You might see their shadow, but you don't see them until they're by. I can't begin to tell you how many times I've been in a race and had someone who couldn't see me cut me off. It's pretty easy to do.
Barr is no victim. She swings the elbow (about 1:42 in the video), then, failing there, she moves hard over (about 1:44) into Saugus, so hard, in fact, she loses her balance and falls.
You're seriously trying to say that Saugus decided her best course of action (all the while closing rapidly on Simi) was to get mixed up with Simi--from behind?! At the rate she was going, she was clearly going to get around, and the less contact the better so far as Saugus would be concerned.
Simi parent?
I have no rooting interest for either team and was skeptical about the DQ until seeing the video.