On leaving ArtsEd, Dee began her career as a dancer, subsequently moving to Rome, Italy where she taught dance, took singing lessons, and learned to speak Italian.

[8] This led to leading roles in musical theatre, including Sarah Brown in Guys and Dolls, Ellie May Chipley in the award-winning Royal Shakespeare Company and Opera North production of Show Boat at the London Palladium, Bombalurina in Andrew Lloyd Webber's Cats, Duke Ellington's Sophisticated Ladies, Claudine in Cole Porter's Can-Can, and Ado Annie in the national tour of Oklahoma!.

Dee's portrayal of Carrie Pipperidge in the 1993 Royal National Theatre's production of Carousel earned her an Olivier Award for Best Performance in a Supporting Role in a Musical.

This began with Paul Todd's fringe production of Between The Lines for which Ayckbourn wrote song lyrics and was followed by Dreams From A Summerhouse at the Stephen Joseph Theatre in Scarborough.

She followed this playing Masha in Brian Friel's translation of Chekhov's Three Sisters and Edyth Herbert, opposite Tim Flavin in the George Gershwin musical My One and Only, both at the Chichester Festival Theatre.

As a result, in 2003, Sir Peter Hall asked Dee to star in his season at the Theatre Royal, Bath, playing Gilda in Noël Coward's Design for Living and Emma in Harold Pinter's Betrayal, opposite Aden Gillett and Hugo Speer.

At the end of the run, Dee helped organise a reading for charity of William Nicholson's play Shadowlands which deals with the relationship between C. S. Lewis and the American writer Joy Gresham.

In 2008 Dee returned to the Open Air Theatre, Regent's Park to play Olivia in Twelfth Night opposite her Carousel co-star, Clive Rowe.

In 2009 Dee returned to Theatre Royal Bath to play Orinthia in George Bernard Shaw's The Apple Cart, directed by Sir Peter Hall, and took over the role of Annie in Calendar Girls by Tim Firth in the West End.

[12] In 2013 she appeared in the Stephen Sondheim revue, Putting It Together for four performances in Guildford, alongside David Bedella, Daniel Crossley, Damian Humbly and Caroline Sheen which subsequently transferred for a three-week run at the St James Theatre, London in January 2014.

From March until June 2014, Dee co-starred in the London revival of Noël Coward's Blithe Spirit at the Gielgud Theatre, opposite Dame Angela Lansbury, who reprised her 2009 Tony Award-winning Broadway performance as Madame Arcati.

The concert also starred Anne Reid, David Birrell, Joanna Riding, Jamie Parker, Anna O'Byrne, Fra Fee and Laura Pitt-Pulford.

Later the same year she played Helene Hanff in a revival of 84, Charing Cross Road at Salisbury Playhouse, co-starring Clive Francis as Frank Doel and directed by James Roose-Evans.

Whilst appearing in the O'Neill play, Dee also performed a special one-off show, Dream Queen in the Sam Wanamaker Playhouse at Shakespeare's Globe, as part of the London Festival of Cabaret.

In the summer she played Irina Arkadina in Torben Betts' version of The Seagull, directed by Matthew Dunster at Regent's Park Open Air Theatre.

In 2016 she starred in the West End transfer of Tony-nominated Broadway comedy Hand to God at the Vaudeville Theatre in London,[14] alongside Harry Melling, Neil Pearson, Jemima Rooper and Kevin Mains.

Dee made an appearance in Jamie Davis’ 2023 London-set three-part drama You & Me for ITV and ITVX, with Harry Lawtey, Jessica Barden and Sophia Brown.

In 2013 she was invited by composer Guy Barker to be the narrator in his new orchestral work That Obscure Hurt which was premiered at the Aldeburgh Festival 2013, as part of the Benjamin Britten centenary celebrations and was broadcast live on BBC Radio 3.

She is a member of the Board of Trustees of the Royal Theatrical Fund and supports a number of charities including Stop the War Coalition, St Mungos, Medecins Sans Frontieres and Amnesty International.

The Blithe Spirit company performed songs by Noël Coward, a charity auction was hosted by Christopher Biggins and there were special guest appearances by Imelda Staunton and Barry Humphries.

Proceeds from the event were donated to Asylum Link Merseyside, Combined Theatrical Charities, Masterclass, Mousetrap, the Noël Coward Foundation and the Royal Academy of Music.