I seem to remember Nyssa (http://en.wikipedia.org/wiki/Nyssa_(Doctor_Who)) being rather quiet, though she wasn't really shy. I can't remember if this came up in canon, but I wouldn't be surprised if she had a soft spot for animals. She did end up leaving the Doctor in order to turn a space station into a hospital and free enslaved guards, so there's a noble humanitarian streak in her.

If it makes you feel any better, I can't see the Doctor choosing me as a companion either. He'd probably pat me on the shoulder and say I was needed more on Earth. *g*