Bancho "graduated" from her position as Ayu's nail artist. (Or at least, that's how I think of it. Like how Keizo Kuroda left Ayu's hair/make team in 2006 or something but still attended the AT10 afterparty... haha.)
Now, Bancho's former assistant nail artist [Minazo] is Ayu's main nail artist. The switch happened when Ayu went to London with the two of them, and at that time Bancho was just around to have fun with Ayu, haha. I'm pretty sure they're still buddies... but since Bancho doesn't work for Ayu anymore, we don't see her often.
http://ameblo.jp/miurakanako/
Bancho's new blog if you want to keep up with her.