In 2000 Bruni took the role of Tanya in the drama Metropolis by Peter Morgan. She co-starred in the sitcom Believe Nothing as Dr. Hannah Awkward (a professor of pedantics) alongside Rik Mayall. The series was written by Maurice Gran and Laurence Marks. In 2002 she appeared alongside Bill Nighy in the successful return of Auf Wiedersehen, Pet. She played Alice in Passerby by Tony Marchant, directed by David Morrissey.

Bruni portrayed the Empress Catherine the Great in the 2005 television documentary Catherine the Great. She also played the role of Sarah Woodruff in the BBC version of The French Lieutenant's Woman, narrated by John Hurt and repeated on BBC Radio 7 in February 2009. From 2009 to 2012 she played Gail, the girlfriend of Jeremy's love interest, in Series 6, 7 and 8 of Channel 4's Peep Show.

In theatre, Bruni spent three years at the Royal Shakespeare Company where roles included Esmeralda in Camino Real, directed by Steven Pimlott. Bruni starred as Jean Rhys in The Shared Experience production After Mrs Rochester (Sydney Theatre). She played Lady India in Ring Round The Moon (Playhouse Theatre), choreographed by Wayne McGregor. In 2013 she played Claire in Yes, Prime Minister (Trafalgar Studios) written and directed by Jonathan Lynn.

In 2015 Bruni performed in Donkey Heart and the one woman show Before You Were Born, both by Moses Raine, directed by Nina Raine at the Trafalgar Studios. In 2016, she starred in the Steven Berkoff double bill Lunch and The Bow of Ulysses (Trafalgar Studios), directed by Nigel Harman. The following year, Bruni appeared as Goneril in a production of King Lear in the Globe Theatre.