Wow! I really have nothing negative to say about this piece. Her right foot is turned at an awkward angle, but this is absolutely perfect!
I'm not sure I like the pink in her hair, just because it's not quite dark enough to be used as a shadow. The middle pink isn't, at least. THe darkest is perfect.
The shading is perfect everywhere! Her hands are cute and proportionate, and I loove her shoulders/neck. You did that really well.

I'm not sure I like the way you shaded her buns, but that's just me. c: Maybe you used too dark of a shadow there or something.
I'd probably add some shine to her hair, as well, but that's up to you.
Her skirt looks a bit fake, like it's molded there or something, but I absolutely love the shading you used there. Ahhh! Teti! stop improving! ;_;

I really have nothing more to say! Great job <33

Excellent colours. Full of colours! Deep and brighty colours! The Serena's expression always tender, shy and lovely. So well done. The pose belongs so good with her expression, the lines add a good motion, movement, the skirt in motion too looks fantastic to this one, even his hair expresses motion! "too much movement?" No, the background is static, that's add some balance. I dislike the rabbits ears (look like knife) but that's only my imagination don't care. I agree with the other comment about the feet, just that. I would like you own the high - resolution size (big size format) in your computer then save it in safe! could be a good printing.