During the Third Task, Harry gets through the maze a minute quicker and steps in as soon as ImperiusedViktor starts to torture Fleur. This means that she is shaken, but otherwise fine rather than eliminated from the task. In the face of unknown danger, shocked after being subjected to an unforgivable and remembering that Harry had already saved her sister, Fleur proposes that they work together to get out of the maze as quickly as possible. It was not easy, but they made it through traps and obstacles, both solving at least one problem the other had no idea about. They decide to share the victory (I guess that leaves Cedric as spider food... Anyway...)
They arrive at the graveyard, and while Harry is confused, Fleur realises that something is amiss.
"Kill the spare!"
Unfortunately for Wormtail, that gave the trap away and Fleur dodges out of the path of the killing curse while Harry gets his wits together. Harry attacks Pettigrew just as he had Fleur cornered, who takes advantage of the distraction and kills Pettigrew (would be too easy if he could be interrogated, could be unintentional/bad fall).
Since they don't know where and what Babymort is and whether he's armed or not. they decide that the best course of action is to get back as soon as possible. One portkey trip later, they are faced with a jubilant crowd and it takes them half an hour to tell Dumbledore that something had gone wrong since the judges secluded themselves to debate if there can be two winners.
Dumbledore investigates but comes back empty-handed after some time, finding only Moody's cloak. While Dumbledore deals with that, Harry and Fleur are delivered to the hospital wing and patched up. Which leads to late-night talking about what the hell they had been through.
As dawn is breaking, both are utterly exhausted but have decided to stay in touch over the summer. Fleur was thinking about getting a job in London anyway, so trips to Surrey aren't a problem.