Evie (Julie Walters) is not dying of cancer; it was a made-up story to force Ben (Rupert Grint) to stick with her through their trip to Edinburgh. Laura (Laura Linney), Ben's mom, jealous of her son's friendship with Evie, interferes with it and makes Evie believe that he simply doesn't want to see her anymore, so he could stick to play the part of the eucalyptus plant at the pageant. He subsequently realizes it, and goes to Evie to clarify things, apparently with no luck.
However, throughout the pageant, Evie shows up and makes a roaring entrance, by reciting, God-like: "I've come for my son!", and gives a show-stopping, ad-libbed moment that grants her a standing ovation. And while she and Ben walk off the theatre, Laura tries to manipulate him once more to do what she says, but he rebels against her, and also rubs on her face her secret affair with Peter (Oliver Millburn). At the same time, Mr. Fincham (Jim Norton) unexpectedly drives his car over her, to which she miraculously survives.
Later on, it turns out Ben's parents will divorce, Ben no longer fancies his dream girl, Sarah (Tamsin Egerton), and he goes to visit Evie one last time to say good-bye -he is going off to college in Edinburgh- and read her a poem he wrote; they part in sweet terms.
Thanks Dr Mat!