Dont think Rochelle could know what others did so her explanation that she wanted other two to do the task was lame. By pressing the button she either put the other one (if one of the two pressed the button) or two of them to do labor, or two from outside to do the labor. So she clearly saved her from all possible options.
Her explanation in this situation did not make sense at all that she did not want to make someone from outside to to the job.
She was happy and clapping when BB announced the result because she was safe and that is what her plan was.
On top of that, she claimed to Keith that the other two were not going to press the button (lame assumption). In my analysis that was smart for herself but guess who is getting nominated next week - Roch (from Mandy and yuvika and their well wishers).
Not only that she told Keith that Yuvika is dumb so she wont do anything. So far, Yuvika is playing a safe and fair game and making good decisions, IMHO.
Even Rimi knew what happened - Roch is loose cannon and needs to be diplomatically tamed.