The 23-year-old actress stars in Sofia Coppola's The Bling Ring, which premiered at the French Riviera festival. Emma plays a celebrity-obsessed Los Angeles teenager who, with a group of friends, burgles Hollywood stars.
With a thick Valley Girl accent, it's a character far from the wise-beyond-her-years Hermione of Harry Potter.
At Cannes, Emma told reporters that while she remains proud of her work on the Potter films, they now feel long ago.
She said she's now "re-enjoying" transforming into new roles. Making The Bling Ring, she said, was much easier since she's used to reciting lines "people know by heart.
Keeping her 7 million Twitter followers updated about her Cannes visit, she wrote: