I've been working on this awhile now...trying to figure out the players. Rather than place this post in the SOTS3 where some of this is also being discussed, I'm putting it here for the continued on-going analysis of the future waterball chal.There *is* a second Mystery Woman(MW2), as also noted by VG, who appears on the right side of the frames in the Sabrina waterball chal scene of so much analysis. This is a female and she has light hair(could be blond hair that is wet or brown hair w/highlights. No buff is seen on this MW2.
The waterball scene appears to show blue buffed Sabrina trying to either block or take-away the ball from orange buffed MW1. Unknown buffed Mystery Woman2(MW2) appears to be either also trying to take the ball away from orange buffed MW1....or she's there to help MW1 from being dis-emballed(sic):-p by Sabrina. My guess it's the first. In which case MW2 is a blue-buffed partner of Sabrina.
Here's some frames of MW2...
And a closer view....
So altho we don't know which color buff MW2 has on, we have these possibilities narrowed down via hair color: Kat, Kim or Chelsea.
AND...there is an image of orange buffed Mystery Woman1(MW1) that can be further analyzed. MW1 *does* have black hair which can be seen emerging from behind the left side of Sabrina's head. It is not noticed in the video at normal speed but can be seen in a frame by frame analysis of the video clip. The hair is not Sabrina's that is just moving around as it is a darker shade of black and emerges as a formed round shape inconsistent w/any hair of Sabrina flopping around.
Here's a frame by frame video clip w/IDs for your review and analysis.