Jeanie DID screw Ferris over ...
... inadvertently.
Because she was hauled off to the police station, her mother had to come pick her, thus losing the Vermont deal. When scolding Jeanie, the mother tells her that she was going to use the commission from the Vermont deal to buy Ferris a car — something he's been wanting for the longest.
So, in a sense, Jeanie did achieve some sort of "victory" over Ferris after all.