Logic dictates that just like everyone else in Equestria there is a version of them in the Equestria Girls universe, so where is the original human Sunset Shimmer? I'm curious if there are stories that explore this.

There is a FimFic by JunSonic using the character of the Real Human Sunset Shimmer being stuck in Equestria if I remember right...

In my personal head canon, Sunset 'put away' her human self as soon as she came to the EG universe.

4038458 thank you.

4045628 It looks interesting, Putting it on high priority.

4045914 You're welcome.

Check out Yukito's "The Misadventures of Sunset Shimmers" -- old-ish, but pretty good.