After taking a short course at the Central School of Speech and Drama, Titmuss made her West End acting debut in March 2006 playing a prostitute with a multiple personality disorder in Two Way Mirror by Arthur Miller, at the Courtyard Theatre in Kings Cross.
In 2006, Titmuss filmed a small role in the major motion picture Goal! 2. She was also offered a role in a remake of Galaxy of Terror, a 1980 horror movie set on an alien planet. She turned it down upon learning that her character would be molested and eaten by a giant moth.
Titmuss was due to have been the subject of a theatre production in a musical satire entitled Being Abi, performed by students in her home county of Lincolnshire. Devised by pupils at Boston College in May 2006, it was scheduled for a three-day run before being cancelled by two of the performers' concerned parents, who objected to some of the production's content.
In February 2007, Titmuss won a Fringe Report Award for Best West End Debut for her role in Two Way Mirror.
She appeared as a celebrity on reality series Deadline with Janet Street Porter as an editor on ITV2. The show followed a number of celebrities as they attempted to produce a celebrity-based magazine each week, published as a supplement to Closer magazine. Titmuss was the fourth celebrity to be sacked from the show. She has previously guest-presented shows on Virgin Radio, MTV and LBC radio.
Titmuss appeared in the second series premiere of Rob Brydon's Annually Retentive, which aired 30 April 2007 on BBC Three and as a character called "Gezebelle" in an episode of Katy Brand's Big Ass show, a new sketch comedy series for ITV2.
From 26 February to 23 March 2008, Titmuss appeared in the black comedy Fat Christ at the King's Head Theatre in Islington, London and is due to appear in the touring play Seven Deadly Sins Four Deadly Sinners.
She has been cast in small roles in British independent films Do Elephants Pray? and Mixed Up. In 2008 she played the role of the 'Mysterious Girl' in Beat 24 Films UK independent feature film 'Frontman' Frontman IMDB Page and Official Site of the film showing photos of Abi on set.
In 2009 Abi was cast in John Godber's play 'Up N Under' to celebrate it's 25th Anniversary at the newly refurbished Hull Truck Theatre, Hull. Abi played the role of Hazel the fitness instructor, starring alongside Jamie Crossley (formerly Gladiator "Hunter") and soap actor Lewis Linford (Lee Naylor in Emmerdale)
From November 2009 Abi appeared in Shakespeare's Macbeth, playing the character of Lady Macbeth with the Seagull Rep. This production opened the Seagull Theatre, Pakefield, Lowestoft before transferring to other East Anglian venues including; The Cut and Halesworth, Bungay's Fisher Theatre and Sudbury Arts Center, until December 4th.