Sandhya most certainly earned the fate of going home. Respective toward all that is deemed fair, having one's work -- of more than two dozen designers -- determined "the worst" would only dictate a sensible exit from the competition. Moreover, to be judged "the winner" should result in, perhaps, a time-oriented advantage during the next challenge: all others, for example, would be required to end their work day two hours early whilst the latest winner may continue working.
Further, it appeared evident that Carrie and Hernan, while not exactly the cream of the crop, are simply more adept in terms of overall ability (to say nothing of Sandhya's unwilling nature for working as part of a three-person team). Any thoughtful, objective viewer would sense a whiff of inequity per the directive that says Sandhya cannot be sent home. As a result, it seems natural that team-oriented challenges allow for too many possibilities of a designer getting railroaded.
By default, the art of design (be it clothing, buildings or furniture) is inherently an individualistic endeavor. Any sort of activity under the "team" umbrella is akin to focusing upon areas of tangential importance. One can be hopeful that the producers of PR are dealing with an avalanche of negative feedback in moving toward (finally) eliminating any such group or team activities. While each designer truly is unique, there should never be a situation that compromises one's own efforts.