Spoiler Space / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / Everybody's awarding kudos to Stacy in FLM for talking back to Tiffany when Tiffany deserved it. I agree, but let's face it. Tiffany is not a particularly intimidating person. Sandi has always been the one who could make Stacy cave in with an ugly stare.
To me, the high point of Stacy's assertiveness so far was in the next-to-the-last scene of FLM when Quinn disagrees with Sandi and Stacy says "I agree with Quinn." Then Tiffany (who probably felt the need to make up with Stacy at that point) says "Me too." With the rest of the FC united against her, Sandi is forced to modify her position.
Steve Cross