User blog comment:Rachel6598/Hermione and Bellatrix: The Cruciatus Curse/@comment-2089216-20110720074736

In the book, Hermione gets tortured by the Cruciatus curse (hence why it is on the page). However, the filmmakers decided against that for the movie, and chose to have Bellatrix carve "Mudblood" on her arm with the dagger. Her mouth is near Hermione's arm because she moves her head over to carve into her. It's just the positioning of the camera.