Dear celestia this made my heart explode, i honestly have very little bad things to say about this.
The lighting and shading is just fantastic and the colouring is perfect, if there ever was something wrong with this then i just don't have the eyes to spot it, you've really managed to capture to cute art style of the show and increase its cuteness tenfold.
This is one of those rare perfect pieces of art that you only find from extraordinary artists.
The only thing i could really say is to improve the background, i assume she is meant to be lying down in a grassy field or something so you could have added a few grass tufts.
I got a minor case of diabetes from this. The only thing I can find that is out of place is the shape of the left front leg. It is rounded from both ends, making it look less like a hoof and more like a weird egg thingie. I can see a line that probably was meant to fix it, (It is pretty faint) But you probably missed it when you were coloring.
Other then that, it is great. I couldn't help but get a giant case of D'awwww.
Either way, I am not actually a very good artist, so feel free to ignore me. Have a great day!