After The Summer I Turned Pretty season 3's wedding is called off, Belly travels to Paris.
The change happens in episode 8, “Last Kiss,” when Belly admits that she still loves Conrad and realizes she cannot go through with marrying Jeremiah. She decides spontaneously to leave for Paris and sees Conrad at the airport before boarding her flight.
Paris then becomes the setting for the final stretch of Belly's story. In “Last Call,” she learns that there is no room for her in the exchange program, but she remains in the city after meeting a group of Parisians. She supports herself with two jobs while continuing college classes online.
The location is distinct from Brussels, which is where Conrad is traveling for a conference in the finale. Paris is Belly's destination; Brussels is Conrad's onward destination after visiting her.