Well done on the picture. Three elements really make this picture for me.
First is the lighting, the fact that is comes off as an incomplete cone of light. We don't get to see it the harsh line of where it meets the left hand side and draws my attention nicely to the reflection. More than anything is how you use the light source and it's realistic shading to bring together the other elements of the picture. Thinking about it, the effect creates a sort of layering in how the impressions hits me. The layers are set from bright colors to darker ones.
What gives the impression as real is the reflection of Pinkie. Really, because it's recognizable as a canon outfit of Pinkie, it sets the impression as something I already believe to be Pinkie. It seems, vibrant, alert and attentive. This is perfectly contrasted by the Pinkamena. Her slouch shows her to be tired. Her straight hair doesn't have the chaotic flare of her counterpart. Throw in that I see her from the back and can't engage her, it lets the imagination fill in the blanks.
The best part is that it's a picture that seems to have a story to it. Works like that aren't limited to just being an assembly of shapes and colors, and let the audience countinue to expand their emotional investment as their mind crafts the story. Good work and keep drawing.