How does Marguerite react when Chauvelin asks for help to unmask the Scarlet Pimpernel?

When Chauvelin requests Marguerite's help she refuses him.

“What you propose is horrible, Chauvelin,” she said, drawing away from him as from some noisome insect. “Whoever the man may be, he is brave and noble, and never—do you hear me?—never would I lend a hand to such villainy.”