Doroa is the second eldest child of the King and Queen of Psycadon, younger sister of Jumbo and older sister of Saran.
History
Unlike most Psydonian's, Doroa isn't that keen on violence but hides this fact from her parents with only Saran and Jumbo knowing. Although they consider the Time Lords to not be their friends, Doroa didn't reveal that she knew the Doctor was on Psycadon.
Behind the scenes
Doroa along with Saran were planned as one-off characters, only appearing in The Traitor but their popularity with the readers has lead to a second appearance being written featuring them.