This is my first time to Critique and english is not my first language so do not blame me, please...
My attention is drawn to the dress. I like it because it is smooth and wavy like a Sailor Senshi fuku (costume). I also like the shading on the dress. You kept some elements from the Sailor Senshi fuku, which I like because she is in fact a Sailor Senshi!
The pose is interesting because she looks like she is going to invite you to dance with her! The pose also make her look elegant.
The background is owerhwelming, in a positive way. The colours have the right amoung of pallidnes for my taste. I like the pattern because it reminds me of Takeuchi-sensei's pictures.
The things you can improve is her eyes. I think the left eye are a bit too far to the left. Since her face is seen from the side you should also draw the left eye seen from the side. It is difficult to draw eyes from the side but I am sure you can do it if you try. I also think the hair could be more wavy.
The color choices are fabulous; I love how she's so pink and that's pulled into the background, but there's enough other colors so it's not overloading the senses.
For the face, I would elongate it slightly and add a bit more roundness (emphasizing cheeks, chin, etc) so it wouldn't have such a "V" shape and the features would sit a little more naturally. The right arm should curve a bit where the elbow is. As well, the shoulders need to slope slightly more to add in the collar bone, so the breasts rest lower.
You have a really good handle on ruffles. The dress is very detailed while still being simplistically cute. Good job.