She came to prominence after playing a variety of characters in sitcoms, including The Royle Family (1999–2000), Two Pints of Lager and a Packet of Crisps (2001–2009), Gavin & Stacey (2008–2010, 2024), and Benidorm (2009).

Her film credits include Tower Block (2012), Quartet (2012), The Huntsman: Winter's War (2016), and The Railway Children Return (2022).

Smith has appeared in the West End musicals Little Shop of Horrors (2007), Legally Blonde (2010), Funny Girl (2016), Joseph and the Amazing Technicolour Dreamcoat (2019), Shirley Valentine (2023), and Opening Night (2024).

[2] She later attended South Axholme Comprehensive School;[4] she was a member of the National Youth Music Theatre from 1995 to 2001, performing a number of understudy roles in productions such as Bugsy Malone, Pendragon, and Into the Woods.

This was followed in February 2003, when she appeared in Heartbeat's sister programme The Royal, where she played the part of Francesca Wheeler, a teenage girl who was suffering from leukaemia in the episode "Immediate Care."

In 2004, she made a one-episode appearance in Mile High as Suzy, an airport cleaner who impersonates a flight attendant in an attempt to become cabin crew.

[citation needed] Smith played Cleo Martin in Love Soup (2005) and starred as Michelle, a hypocritical nutritionist, in three series of the sitcom Grownups (2006–2009).

Since 2009, she has played Joey Ross in special seasonal episodes of Jonathan Creek, namely "The Grinning Man" (2009), "The Judas Tree" (2010), and "The Clue of the Savant's Thumb" (2013).

Titled Sheridan, the one-off special presented by Alexander Armstrong saw her performing some of the songs from her album, and talking about her life.

[16] In December 2017, Smith starred as evil step-mum Sheila in the television adaptation of David Walliams' children's book, Ratburger.

Critics generally were positive of Smith, with one reviewer for The Independent praising her performance as "so much flair and vulnerability" and rating the show 4/5 stars.

[31] Smith originated the role of Elle Woods in the musical version of Legally Blonde in its transfer from Broadway to London's West End in December 2009.

[32] Ex-Blue boyband member Duncan James played opposite Smith until June 2010, when he was replaced by Richard Fleeshman.

Other cast members Smith has performed alongside include Aoife Mulholland as Brooke, Denise Van Outen as Paulette, Peter Davison as Professor Callahan and Alex Gaumond as Emmett Forrest.

[33] Her performance was well received, The Daily Telegraph describing her as: "blessed with vitality, warmth, great comic timing and sudden moments of touching vulnerability.

[37][38] Between March and June 2011, she appeared in Trevor Nunn's production of Flare Path at the Theatre Royal, Haymarket as Doris, a former barmaid married to a Polish count in the RAF.

The production was part of the playwright Terence Rattigan's centenary year celebrations and also starred Sienna Miller and James Purefoy.

[citation needed] Shortly before collecting her award at the ceremony on 17 February 2013, Smith performed the original song "Stagey and Proud", which was written by Chris Passey and Amy Carroll.

[43] From September to November 2013, she starred alongside David Walliams in a West End production of A Midsummer Night's Dream, as part of Michael Grandage's season of plays at the Noël Coward Theatre.