Yeah, I was actually practicing poses and she was one of the sketches. I later drew SweetieBot and felt like they needed to be in one picture, so I rushed this image (hence the cellshading - I'm usually no fan of cellshading images)
Just a tip: the thing about robots is that, superficially, they look exactly like ponies. That's how they blend in. So, gotta find ways to make it obvious Sweetie Belle is a robot in full view, but it's hard to tell from a thumbnail.
Unless, of course, you do something more abstract; say, a Sweetie Bot who looks a lot like a pony version of EVE walking by a mirror, and her reflection is that of biological!Sweetie Belle.