Can you help me remember this character? (DW)

Okay, so I was watching “Who do you think you are?” and it was with Twiggy (Leslie Hornby), and she reminded me so much of a character in one of the Doctor Who episodes.
The problem I have, is that I can literally imagine the character in my head, and all that, I JUST CANNOT FOR THE LIFE OF ME PLACE HER!
I know the character isn’t actually portrayed by twiggy, but the actress looks a lot like her.
I am also pretty sure that she appeared in an episode with David Tennant as the Doctor.

I can remember the character as being frightened.
Possibly one of the game show type episodes? I’m not sure.

It is really starting to bug me, because I can picture it so clearly, but can’t place it.
PLEASE HELP!