Stacy is taken aback by Marcelo's question: is there something sinful about telling everyone that she took ingredients from the restaurant to make that original stroganoff that pleased her beloved boyfriend?

No, what is sinful is Stacy's uncontrollable desire to go to the beach in an illogical expectation of finding Marcelo only in swim trunks, so the two of them will mate worse than dogs in the hot sand.

And what's dangerous is the fact that Simeon is almost guessing by deduction that Stacy is hot for Marcelo.

After all, this goes through Stacy's mind at lightning speed, she just smiles mysteriously and replies, "No, I'm being silly and irrational....