I looked over the entire picture several times trying to find her, completely unable to see her, and then just laughed hysterically whn I finally did find her.
I have to say this is a parody of a lot of things. Reimu, Marisa, Mokou, Reisen, Youmu, Patchouli, and Keine seem to be a parody of a MMO style game and its possible that Sakuya, Alice, Meirin, and Sanae are also part of it. Yuyuko is definitely a parody of the Marsh-mellow Man from Ghostbusters.