They tried a little too hard in that episode to convince you Monica was going to flip.
My only fear now is that Monica wins on spite votes against Tyson. Or, if Laura comes back there's a stronger argument for Monica to flip. Laura "Hey, I'm the favorite for the last immunity challenge. I win, who are they going to vote out? And besides, wouldn't you rather be the only non-Moret in the final than be against the two obvious best strategic players?"
I do like the rock-drawing system for ties. Remember there were two ties in the first three seasons, then none between Paschal being screwed in season 4 and last week. The goal of the rock drawing system is to prevent ties, and it did its job extremely well.