It's a bit like what happened to Martha on Doctor Who, come to think of it; she was never allowed to stand as a character in her own right because her series was overshadowed by the constant mentions of Rose. It's like that, only Rose comes back to join the TARDIS team halfway through the series, and she doesn't really have much to do plot-wise but pulls all the focus from Martha just by being there.

PLEASE LIKE ME, SHOPKEEPERS, I'LL BUY SO MANY UNNECESSARY HATS IF I HAVE TO