Darla von Karlsen was a humanoid woman whom the Eleventh Doctor met on Skaro after receiving her plea for help. She told the Doctor that her daughter, Hannah, was trapped in a Dalek prison camp and that Darla had escaped from the camp. The Doctor was suspicious, and rightly so; the Parliament of the Daleks had actually turned her into a Dalek puppet and given her the mission of securing the Doctor for their plan to destroy the Dalek Asylum.
After the destruction of the Asylum, and all of the information about the Doctor erased from the Dalek Pathweb by Oswin Oswald, Darla could not recognize the Doctor, like all the other Daleks in the Parliament. (TV: Asylum of the Daleks)