20 Biggest Things The Harry Potter Movies Left Out
16. Marietta Edgecombe
In The Book
Marietta Edgecombe was a reluctant member of Dumbledore's Army, joining mostly because Cho Chang went along, who would eventually betray the group in fear that her mother's Ministry job would be in peril. As a result her face erupts in boils thanks to a jinx placed on any members who gave up the DA/s secrets.
In The Film
She doesn't exist: at least not in any important way, and Chang forces nobody to join the DA against their will. It's Cho herself who gives up the DA when Umbridge uses Veritaserum on her.
Was It A Positive Cut?
It made a villain of Cho Chang, albeit temporarily, but Marietta probably wasn't all that important to the plot anyway. The very idea of her being allowed in the DA when she "really didn't want to be there" was just ludicrous and asked for trouble.