If you don't mind a bit of critique, there's two things that I think could be done even better. Sweetie Belle still looks like a filly here to me; until I read in the description that this is an older her, it never occurred to me that she might be any older than she is on the show, and even now she still looks that way to me. Also, her pose is a little static: it does look like she's taking a walk, certainly, but it also looks like she's just stopped dead in her tracks, perhaps (judging by her expression) because she heard a bird sing a beautiful song and wanted to listen to it. Perhaps that's intentional, but I thought I'd point it out anyway.
But nonetheless, I really like it! She IS adorable, and the background is very nice, too; I really get that relaxing "cool and quiet winter morning" vibe from this.
Weeell, the commissioner asked for a slightly older or teenage type Sweetie Belle. Wasn't sure how to differentiate it so much.. And yeah.. I was having trouble getting it to look like she was moving. Still need to get the pony walk cycle down pat.