Bio: Tama lives next door to Sensei-san who takes care of the faries. She often tells them about things herself. She knows quite a bit, but she still has a child's view on things as well.
Opinion: She's cute for one thing. And she has the the fang. Plus she provides a lot of the fuel for the events in many episodes. Without her around to tell the faries things, they'd have to less to react to. She's the main link in the chain so to speak.