Hifumi Takimoto I - Mk 2

This is my first critique, I hope this will be useful~

First of all, I really like the overall feel of the image. Hifumi is absolutely adorable, you captured her character really well. Everything from the insecure pose to her embarrassed expression works together to make her look super cute.
I like that you used different colors for the light coming from the sides an colored the linework to match the shading.

There are a few things that I think you can improve on to make this image even better: The shading is a bit inconsistent, the dress casts a shadow onto her legs, but there is almost no shadow below her arms, her head or the hair. And while the skin was shaded flat, there is more realistic shading on the dress and her ribbon. There also is some indication of texture in the highlights of the hair but not really anywhere else. In my opinion, it would be better to stick to one way of shading throughout the entire piece.
The ponytail probably should be a bit more straight as it is pulled down by gravity, there is no other indication of wind or perspective that would explain why it is that far off to the right.
I would recommend to change up the widths of the individual bangs of the front hair. If you look at the original character design, you can see that there are some bangs that are wider surrounded by really thin ones. The way you drew them is a lot more even, which is less interesting to look at.
The dress has sharp corners at the bottom, which makes it look flatter than the shading suggests. I would either reduce the folds if you were going for a flat look or round up the shape to show that the dress is wrapping around her and give it a bit more volume.

Additionally there a few things that I personally would change, but this mostly comes down to individual style so take this more as suggestions than objective critique: I think using colors with higher saturation (e.g for the shadows on the skin or for the ribbons) would fit the upbeat tone of the series better and could help to add some visual interest. Varying the width of the lines a bit more could make the drawing stand more, for example, you could add a thick outline to create a flat cut-out look or hint at shadows by making one a small part of a line thicker.
There are a bit too many highlights, e.g. I would prefer to see some indication of the hands.

Overall, most of the things I pointed out are minor issues or really just nitpicking. I think the image turned out really good and I hope some of my ideas can help you to improve even further.