When Fleur shows up at Number 4, Petunia warmly welcomes her and invites her in for tea, going all out to make a good impression on Dudley's new girlfriend. Her son managed to find quite the looker after all, and she doesn't want to mess things up for him. She asks all kinds of questions and Fleur gives Muggle appropriate answers. So Fleur tells her how she works in a London bank, has been over in Scotland for an exchange year and so on. Petunia really starts to like this young woman.
Half an hour into the meeting, Harry returns "home" and Petunia's world is shattered when Fleur kisses Harry in greeting.