It was pretty smart actually.
Once Amanda (truly a bad liar) confirmed to Parvati that they weren't voting for her and actually voting for someone else, she gave the idols to Sandra & Jerri.
That way, with Danielle immune and Russell supposedly with the Heroes, there was no way that a villain would get votes. Now the Pagonging can begin (unless someone flips that is).
Also, when she gave the first idol to Sandra, she saw the Heroes laugh, so she knew they weren't voting to Sandra, so then she gave the other to Jerri, and there looks confirmed who they were voting for. Note to contestants, always keep your poker face on until after the votes are read. Also, by giving Sandra an idol, perhaps it will prevent her from flipping.