She appeared as the evil sorceress Nimueh in the 2008 BBC fantasy series Merlin and as Lady Christina de Souza in the 2009 Doctor Who episode "Planet of the Dead".

[2] Her character's key storylines in the soap included discovering Kat Slater (Jessie Wallace) was her mother and not her sister, as well as being involved in the cover up of the murder of Den Watts (Leslie Grantham).

[4] In early 2007, Ryan was seen as Maria in Mansfield Park opposite Billie Piper for ITV and also as Lila in the film I Want Candy, co-starring Carmen Electra and Mackenzie Crook.

[6] She also learned Krav Maga and sign language for the part (the latter because, as originally conceived, Ryan's character was to have had a hearing impaired sister, but this story element was abandoned).

[10] In January 2009, the BBC announced that Ryan had been cast as Lady Christina de Souza in the Doctor Who special episode "Planet of the Dead", which was broadcast on 11 April 2009.

That same year, she appeared in the comedy film Huge alongside Noel Clarke, Johnny Harris, Ralph Brown, Thandiwe Newton, and Tamsin Egerton, directed by Ben Miller.

[15] Ryan also appeared in Cockneys vs Zombies, a comedy horror film about a team of bank robbers fighting the undead, directed by Matthias Hoene, alongside Georgia King, Rasmus Hardiker and Jack Doolan.

In 2018, Ryan began reprising her Doctor Who role as Lady Christina in her own Big Finish Productions spinoff audio drama series.