Harry Potter and Luna Lovegood walked into Hogsmeade hand-in-hand, looking into each other's eyes.
I hope they trip, thought Cho Chang from her hiding place inside the window of Madam Puddifoot's tea shop. She fumed inside. She had wanted Harry - she had had him for a time - then he was gone. Resisting the temptation to curse him from inside the restaurant, Cho turned back to her tea and chugged it, regardless of the heat that rushed down her throat. She couldn't be any fiery than she already was. Stupid couples, she thought angrily at all the students who sat practically in each other's laps, making out. "Get a room," she muttered under her breath and pulled back her chair with a loud squeak. Ernie Macmillan stopped messing with Hannah long enough to stare at her. "Who put a toad in your tea?" "What are you staring at?" Cho hissed in his general direction, and stomped out, just as Hannah pulled him back.

* * * * *

"Luna," mumbled Harry, "do you know what I was thinking just this morning?" "No, Harry - what?" "Well, you see, Luna" - he fumbled for his train of thought - "I . don't . either ." She giggled at Harry's obvious confusion as he stared at her some more, then just pulled him to her and started making out with him. Again.

Cho was angry. Again. She could see, and also hear everything from the bushes where she crouched. Harry hadn't been that way with her. Should have been. He should have been shocked speechless by the way she looked. She had even heard Slytherins call her stunning.
She got out of the bushes, wand at the ready. Cho had made a lot of noise getting up, and yet neither of the kissing couple had turned. She stared at them, her eyes growing shiny. Why didn't she have any of that? Why? She should!
By that time, she had figured out what was going on. "Get a room, too!" she whispered at Harry and Luna. They REALLY didn't need to be doing THAT in public, thank you very much.
Then she had a stroke of inspiration. Cho muttered a spell under her breath - and Harry and Luna froze in the * very * inappropriate position they had been in.
"HA HA HA HA HA!" Cho yelled, and ran off to petrify more young lovers. She would soon be infamous in Hogsmeade.