The short three-word sentence at the end here is another line with a double meaning. In the plot, the two ladies are simply switching places in the car. But this is the beginning of the role reversal, where Therese starts to be the one in charge of the relationship and Carol becomes her passenger.

The detective is a voice of reason here. Carol resents her husband because he wants to own her, but it appears that Carol feels the same way about her own daughter. She doesn't really love her; she just wants to possess her.