I get the idea that Sandy was thrown from Timbira, partly due to the comment that Tyson has already made about her in first impressions, and the fact she is the old lady of the tribe. I think it might be Candace or Deb (the other older lady) that was ousted from Jalapao to join Timbira. I think Stephen also made the extra effort to make Sandy feel welcome in the new tribe and has his arm around her in the picture.
What bothers me is simply the clothes, though. Everyone is so obviously matchy-matchy with their tribe color. If anyone switched tribes, wouldn't we be able to tell instantly simply from what they were wearing?