Marietta Edgecombe's defection not only betrayed Dumbledore's Army, but ultimately doomed Harry and Cho Chang's relationship.
MARIETTA EDGECOMBE IS THE ONE WHO BETRAYS THEM
In the novel, it's Cho's friend Marietta Edgecombe who tells Umbridge. Marietta's mother's job was to monitor the Floo Network, so Marietta told Umbridge after worrying her mother's job was in jeopardy.
She Didn't Betray Dumbledore's Army
While this might have made the story simpler for the films, it really did Cho a disservice. It was really Cho's friend, Marietta Edgecombe, who told Umbridge. While Cho remained loyal to her friend, she was also loyal to the DA and even came back to fight in the Battle of Hogwarts.
Betrayal and discovery
Shortly before Easter, one D.A. member, Marietta Edgecombe, betrayed them to Umbridge. She was a reluctant member of the D.A., having been brought to the meetings by her friend, Cho Chang.
Cho being the one to out Dumbledore's Army in the film, differs from the events of the book. In the literary version, it is Cho's friend, Marietta Edgecombe, who exposed the army. The betrayal caused Hermione to overreact and cast a charm on Marietta that wrote the word "sneak" in pimple like bumps on her face.
However, the identity of the snitch has been changed. In the book, it was Marietta Edgecombe — a Ravenclaw student who was a close friend of Cho Chang. But the movie went on to pass the torch to Cho herself, making her the one who spilled the beans about where Dumbledore's Army was stationed.
In the film adaptation of Harry Potter and the Order of the Phoenix, the character of Marietta Edgecombe does not appear, and instead it is Cho who betrays the D.A. under the influence of Veritaserum.
When Cho's friend Marietta Edgecombe betrays the group to Umbridge (Cho herself while under the influence of the truth potion Veritaserum in the film), Marietta is cursed with pimples on her face as a result of Hermione's casting a spell on the D.A. membership list.
Mundungus Fletcher was played by Andy Linden in the film adaptation of Harry Potter and the Deathly Hallows.
Harry describes Umbridge to Sirius Black, saying that she's vile enough to be a Death Eater, despite not being one. Umbridge is also depicted to be a prejudiced person, despising half-breeds and Muggle-born witches and wizards to the point of firing Hagrid due to his half-giant birth status.
The explanation is very simple - Harry has a very strong sexual desire for Ginny. He has no such feelings for Hermione. Sex is a fundamental aspect of adult relations. Sex is, in fact, the characteristic that defines the difference between a platonic relationship and a romantic one.
Despite his attraction to the Dark Arts and Voldemort's ideology of wizard supremacy, Snape's love for Muggle-born Lily Evans, Harry's mother, eventually compelled him to defect from the Death Eaters. He then became a double agent for Albus Dumbledore and the Order of the Phoenix.
The Half-Blood Prince - They Finally Get Together
After years of build-up, Harry finally starts to have feelings for Ginny in The Half Blood Prince - and one of the first moments he realizes it is when he smells Amortentia, and it smells like 'something flowery he had smelled at the Burrow'... Ginny's hair!
From an in-universe perspective, there were no Slytherin students because Hermione oversaw recruitment for Dumbledore's Army — since she did not interactive positively with any Slytherin students, she didn't invite any to join.
We all make mistakes, and even though this was a pretty big one, was it still right for Hermione to punish her? Marietta Edgecombe was certainly not wicked, or twisted, or even worthy of the vitriol – and long-lasting scarring – she received as comeuppance. She'd suffered enough.
To save time to explore the most important storylines, Charlie's character was unfortunately cut.
The Head of Slytherin is Horace Slughorn (who left the role to Severus Snape for fifteen years before taking it up again in 1996) and the House's patron ghost is the Bloody Baron.
At different points, Dumbledore possessed all three Deathly Hallows. He won the Elder Wand from Grindelwald, had the Invisibility Cloak in his possession when James Potter died, and wore the Resurrection Stone as it sat in Marvolo Gaunt's ring. Dumbledore's powers are really quite extraordinary!
According to the films, Hedwig's killer might have been Selwyn, who was known to be pursuing Harry and Hagrid at the time since Hedwig's death in the film happened quite a while into the fight when there was only a couple death eaters following them, or it might have been Stanley Shunpike under the Imperius Curse.
In Deathly Hallows, Hermione faced a real test of her physical and psychological stamina. After being on the run from a bunch of Snatchers, the gang were taken to Malfoy Manor, where Bellatrix proceeded to torture Hermione using the Cruciatus Curse.
The two remained friendly afterwards, though for a brief period Harry thought Krum was mad for using the Cruciatus Curse on Cedric Diggory in the maze, but then he learned that Krum had been under the Imperius Curse.
In the film Harry Potter and the Deathly Hallows: Part 2, this duel has some noticeable differences: In the film, Bellatrix casts a blue spell at Ginny Weasley instead of a Killing Curse, who deflects it using a Shield Charm.
Before Half-Blood Prince, Ginny had no love for Cho as she was extremely jealous of Harry's attraction for her – this because Ginny was so obsessed with Harry the whole, if you'll recall.
Voldemort intentionally made six Horcruxes, but when he used Avada Kedavra on Harry, he unintentionally created a seventh Horcrux. Instead of dying, Lily's love for Harry created a counter 'curse' known as Sacrificial Protection and saved Harry.
Amos thanked Harry for returning Cedric's body, and assured him that they did not blame Harry for his death.