Henry was brought up in Peckham, London. She spent some time with the 'Old Vic Youth Theatre', and at sixteen was in the same acting group as Rowan Atkinson at Edinburgh. At seventeen she went to the Webber Douglas Academy of Dramatic Art. Henry later set up a production company, Buster, which still exists although she is no longer involved with it.
As well as her role in Bad Girls she is also remembered for her role as Sandra in the film Beautiful Thing  and has appeared in the British television programmes The Bill, Birds of a Feather, Touching Evil, Cracker, A Touch of Frost, Trial & Retribution as Marilyn Spark and EastEnders, where she played Lorraine Salter, the prostitute mother of the teenage tearaway Mandy Salter. (Henry and Stapleton both appeared in Bad Girls, although not at the same time, as Henry's character had been killed-off by the time Stapleton arrived.)
She had a minor role in British film The Business as the character Shirley, which also starred Danny Dyer (who would later appear in EastEnders as Henry's on-screen son Mick) as the main character.
On 8 September 2006 it was announced Henry would be returning to EastEnders in a different role, this time playing Shirley Carter, mother to Carly and Deano and ex-wife of Kevin. Shirley arrived in Walford in December 2006. Henry took part in the 2008 "WestEnders" Children in Need appeal where she sang alongside other EastEnders cast members. She is close friends with co-star Cheryl Fergison, who played her on-screen best friend Heather Trott. She also took part in a 2008 EastEnders edition of The Weakest Link and appears in the 2010 spin-off series EastEnders: E20. In 2009, her co-star in Beautiful Thing, Tameka Empson (she played next-door neighbour Leah Russell to Henry's Sandra Gangel) would join EastEnders herself, as Kim Fox.