Firstly, the hat looks like it's about to fall off! I've no idea how it can be as it is without sliding off, maybe dropping the top of the hat down, pointing towards her back/flank will make it look less 'physics defied' and more natural. Secondly, I love your sketchy style, but the harsh highlighting of white on her mane and tail looks too rough and rushed against the rest of the image, maybe using shade of white instead will help as it looks like several strokes of paint instead of one natural looking highlight.
However, I am absolutely in love with this scene. Coffee Cup looks utterly adorable like this, the delicate blush on her cheek is barely visible and just oozes of cuteness. The snow is done nicely, it's not too plain nor overly done. Same with the sky too. Seriously a touch more work on that hat and with shading and highlights and this would make a damn good picture!
I'd certainly purchase this as a Christmas Card/E-Card. You should be proud of this. C:
Fast sketch? I like the way you did the snow, the hair seems like its kinda floating in mid space, and the hat looks like you could have taken a minute or two to fix it up, other than that great job very kawaii desu~