Wow, she looks so cute and gorgeous!!<3 I really love how you added the sparkles and bright background~ it kind of imitates her Mercury Bubbles haha! You did a great job on capturing movement in this pic~ especially with the hair and clothing! And she has such a cute expression on her face..so happy ^^ Lovely work with all the blues, she looks great!
On the critique bit...there are only a few minor things~ her head is pretty big in relation to the rest of her body, and the shape of her head is a tad bit disproportionate. It just doesn't look completely natural...maybe try bringing in her cheeks more and looking at people's face shapes for reference?
While the rest of her body is relatively in proportion, the way that her left arm goes to her hand behind her hips is not very jointed...perhaps when you draw your pictures, you would want to set up the shape of her arm to make sure it's aligned more.
Otherwise, wonderful wonderful work! I love the detail and shine you've got going on here ^^ I'll be watching your work! Keep it up!