Actually, I'd lean towards this not being Setsumi. It's by the same artist who does the real thing, yes, and the resemblance is pretty similar. However, there is post #59117, which is the same pic except lower res and with some text, which leads me to think that this is just from some CG collection.
Also note the differencies between this and post #54865 - Mainly, the red instead of blue scarf, shorter hair, different eyecolor, and the size & location of the hair accessory. Not conclusive perhaps, but given that they're by the same artist I don't think there's much of a clear reason you can come up with (save maybe that they're from different timeperiods and the scarf color changes according to school year :p) to explain the differencies, other than that they're probably intended to be different characters.
I see, maybe I jumped too fast to conclusions, when I saw Dr_Fine_Rolo reasons why it was not Setsumi. But I would think this is closely related to narcissu and Setstumi from stage nana is probably based on this girl.
