SOOKIE: Hey, what about Luke?
LUKE: What about him?
SOOKIE: He eats, and Jess eats. Doesn’t Jess eat?
LUKE: What’s she doing?
LORELAI: I think she’s inviting you for dinner.
The original plan after the people from Chicago cancel is for Sookie, Jackson, Lorelai and Rory to have the dinner by themselves. Sookie cleverly asks Luke and Jess, hoping to push Luke and Lorelai together (I think only by coincidence would her plan also push Rory and Jess together).