Hunk said to have proposed last month
The couple are believed to have got engaged last month.
Bonnie, 19, who plays Ginny Weasley, was snapped wearing a gold ring on her third finger left hand at the Gucci Icon party in London on 21 April.
She and Jamie, who plays Gellert Grindelwald, have been dating for 6 months after meeting on the set of the forthcoming Harry Potter And The Deathly Hallows movie.
The 21-year-old also starred in The Twilight Saga: New Moon as Caius Volturi.
Reps for Bonnie and Jamie told Now Online they do not comment about their private lives.
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