Miley Cyrus isn't letting the uproar over her bong use knock her off her game -- in fact sources say since the video of Miley experimenting with drugs came out ... the 18-year old's been a total pro on the set of a movie.
Miley arrived in New Orleans last week to shoot "So Undercover" -- and sources close to the production say hours after TMZ published the video of Miley taking bong hits ... she showed up for rehearsals.
We're told Miley and her co-star -- Kelly Osbourne -- ran through script lines, as scheduled, on Friday. According to our sources ... Miley knew the bong video was out, but "she kept her focus on the movie."
Miley's mom, Tish, is a producer on "So Undercover." It's unknown if she is on set yet ... filming isn't scheduled to begin until later this week.