That Companion meme that's been going around...

Susan
Take Which Doctor Who companion are you? (girls) today!
Created with Rum and Monkey's Personality Test Generator.

You're Susan!

For a fugitive from your own people, you're one of the most innocent of the companions, probably because your grandfather is so protective of you. You bring out the tenderness behind the Doctor's bluster and occasional coldness. You are implicitly trusting of the Doctor, no matter what he gets you and the others into, and your confidence in him helps others rally around him, too. Your sweetness and fondness for humans is the legacy you leave him even after you move on.

Huh. Wasn't expecting that, but from what I know of her, it's a pretty good fit. (I'd kind of pictured the Doctor as being the "cool physics teacher" sort of role model to me. Er, not that I've written lots of horribly indulgent self-insertion fanfic that will never see the light of day thought about it that much....)