OK, you might not believe this, but the Si that I was seeing was in her body movements. In my opinion, Si-users have smooth, competent control over their bodies (every baseball player in the world is SLI), and she was moving in that manner in the beginning of the video.
An example of what I mean can be seen here:
https://www.youtube.com/watch?v=hmcT6ex-214
where the first woman is an EII and she moves like a prancing horse, very smooth and showy. EII's even run like this, IMO.
The second woman is an SEI and all of her moves are smooth and her body is under tight control, as if every muscle is moving from a central, internal command center. Watch her body. She remains centered and the limbs move around the center.
The third woman is an Se-dom and she's kicking the earth as if she's mad at it. Nothing subtle, nothing graceful, just kicks. Boom Boom Boom.
The fourth woman is an LIE, I think, and she's Se-HA, and it looks to me as if she's reciting her moves from a book that she studied. Nothing really natural about her moves.
The last woman in the video might be IEI, and she looks as if she's surprised to have a body at all and she doesn't know what to do with it.
Now watch Ashnikko's moves in this video:
https://www.youtube.com/watch?v=6i01tOMgBDU
She's smooth and graceful, in spite of looking like a spoiled brat.