This isn't supposed to be Sakura. For example, screenshots have shown this woman talking to Sakura Extra. Other official materials describe her as "Unknown/???" or "Mysterious Black Magus." So how exactly should we tag Not!Sakura?
Well, I guess I'll just tag her Mysterious Black Magus(CCC) like the official material did. It will just be a placeholder anyway, until the game reveals who she is when it comes out.
How much ram would one need to color a picture of this size without having the computer explode? Even with 6 gigs, I've not been able to color an image this size. o_o
At this resolution and color depth, you're looking at roughly 121 megs, raw, per layer. I can't imagine how six gigs wouldn't be enough, unless you're running a whole mess of other stuff on your system, or are running a ridiculous number of layers. If you notice, in this image, it's probably just one color layer, or one flat and one shading. There's not really any blending going on here, it's flat swaths of color.