The film, which is based on real life events, follows a gaggle teenagers whose celebrity-obsession leads to high-stakes burglaries.
Mann is playing the mom of two of the Bling Ring members (can you imagine the squeaky-voiced insults she'll hurl at them?) and Broussard will play the male lead.
In addition to directing, Coppola is also writing the film and will produce with her brother Roman Coppola and Youree Henley.
"I'm excited about the young cast we're assembling and I'm looking forward to shooting on location here in Los Angeles," the "Lost in Translation" director told Variety when Watson was announced as the film's lead. Coppola's last film, "Somewhere," also took place in Los Angeles.
Mann has plenty experience playing on-screen mommas (usually with her real-life children). She next reprises her role as Debbie alongside Paul Rudd in "This is Forty," the spin-off of 2007's "Knocked Up."