Freddy gets away with her sass because she's white and (very) conventionally attractive and she is probably narcissistic enough to not see how hypocritical she is. Her ability to sell us this persona as an angelic looking sassy girl is a perfect example of the halo effect and white privilege. A black or brown woman in Freddy's shoes would have been typecast as angry, rude, nasty, too materialistic, glib, you name it. I don't doubt she is cognizant of this bias which is why she's so obsessed with her image, it is her greatest asset, her entire life is dedicated to it, she does her utmost to adhere to the standards of white femininity and beauty to maintain her position of power