I thought that there was some logical growth to Tara's clothes... that in Season 4 her dowdy outfits reflected the fact that she was in hiding, from her family and from the possibility that she might be a demon.
In Season 5 her outfits were improved, I thought, showing that she was more comfortable in her skin, but still living vicariously through Willow.
Finally in Season 6 she was really blossoming (the outfit in OMWF, above, is certainly beautiful) because she was really standing on her own and confident.

Amber is another one I got to meet, do you realize she has perfect recall and remembers her fans by name? She is wicked smart and funny (I love that she is dating Adam Busch, but I don't know why they haven't gotten married! ).