The shading is very good. Especially since you used MS Paint. Overall, it is an amazing piece of art and is very hard to find anything bad but there are a few things that could be corrected.
Her hair seems a little unnatural, but that's just my opinion, actually, a lot of Rarity artworks draw her hair like that, but if you're drawing her completely human the hair would be different.
I think you could have done better with the flower, it seems like its just floating there and her hands are just there, (and could have been drawn a bit better).
Her legs are very nicely drawn, my only critique is that you should define the ankles a bit more, you don't want her to have cankles!
Everything else is good, she isn't sickly thin, ore abnormally fat. Her anatomy is very good. And as I said already, the shading is perfect!
I must clap my hands and say, well done.