Classist life lessons, courtesy of Thomas, a.k.a. Sabrina's daddy:
THOMAS: I like to think of life as a limousine. Though we are all riding together, we must remember our places. There's a front seat and a back seat and a window in between.
That window stands in for—you got it—the separation of the rich from everybody else. The Larrabees sit in the back in luxury; the Fairchilds sit in the front and drive them around. Them's the breaks (or is it them's the brakes? it's a car metaphor).
Sabrina, though, finds the chauffeur's car stifling—literally—when she almost kills herself with carbon monoxide poisoning in the garage. She wants to crawl out of the front seat into the back seat, and grab hold of the money (and the, um, lips) of the wealthy David.
And she does. When she returns to Long Island, her father fails to pick her up, because Linus has taken out the car. He's still in thrall to the powerful—but as for Sabrina, David picks her up in his own car. And later, of course, Linus actually has Thomas drive him and Sabrina out on their dates, which Thomas points out is awkward, and icky, and stop, Linus, you gross dude.
Linus may be a gross dude, but he's Sabrina's gross dude. Thomas thinks that the social classes should never mix, but Sabrina demonstrates that if you're awesome and determined and look like Audrey Hepburn, there's no stopping you from climbing into any part of any car you wish.