Ok here we go, searching for "左城宮 則紗" gives me 40 results on Pixiv, so she's generated enough interest in the Doujin Engine for several artists to have a stab at her. Most of these images show her having somewhat Stag-like horns, the image Totaku linked here happens to have her hair as more generic spikes.
Here is the Pixiv location for that image, and the artist says he got his inspiration from that NicoVideo Drake linked. In fact, just about all these images (from the sample I'm looking at) mention that NicoVideo as their source.
This is a cuter take on her.
This interpretation gives her an armpit outfit. As always, you need a Pixiv account to see those links.
In short, yes it's fake but it's generated enough interest that many artists have had a one-shot at her.