"Green Dam Girl" is a personification of the Chinese government's filtering software.

See also:

http://www.danwei.org/net_nanny_follies/green_dam_girl.php

http://www.hecaitou.net/?p=5770

http://forums.megatokyo.com/index.php?showtopic=1733788&st=50#

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She is almost look like Kawashiro Nitori.

I think that was intentional.