This is a lovely attempt, do not let the rating distress you. We are all here to improve and move forward.
I would like to start off by saying that you are a talented artist, I have looked through your gallery and I know without a doubt that you will improve greatly with each piece you do.
I will narrow down each area so we can discuss the flaws and ways to fix them up; as well as some tricks and tips.
When drawing anything, you need to know at least the basic anatomy of it's original form depicted. Meaning if you were to draw; in this case a human but in your own style or a style such as Anime here. You will need to know the basics of natural human anatomy, and it will help greatly with proportioning as well as detailing a piece. This goes for anything you draw, from people to animals and even objects. Which is why jumping straight into a style such as Anime is not a good idea until the basic knowledge is there for human anatomy.
For the head structure it looks rather flawed. So to fix this, when drawing next time begin with the basic drawing guides so to speak. Circles, lines, squares, etc. Basic shapes and they will help form a rough skeleton so to speak and will help in the over-all forming. So when drawing next time, begin with a simple circle. It does not need to be a perfect circle, just a rough rounded shape, then follow over with the guide lines to help align the features of the face. (i.e eyes, nose, mouth, hair, etc) one straight vertical line down the center, (which the center varies depending on the positioning of the head itself.) a horizontal line near the center, another horizontal line roughly 2 inches above the middle line, and finally a last horizontal line near the top of the circle depicting the hairline; which varies depending on the size of the head but will be generally around the same area.
The vertical line will assist in keeping the features of the face in their respective places by helping you see the center of the face. The horizontal lines will assist in nose and eye positioning. Noses come in all different shapes and sizes, as do eyes. They come spaced close together, in the middle or out more it all depends on how you wish for the person to appear.
Beneath the circle you are going to want to create the jaw, and chin area.
Since this is a little easier shown than explained, and I do not know if you are more so a visual learner or by words; I sketched out a quickly little reference guide for you:
Terribly sorry about the Anime version, as you may see that is not necessarily my genre but I hope it can at least get the message through as to what it would look like roughly
I do know that eyes in the Anime genre vary in shape and size, so here I can mostly just suggest some changes really. I am not 100% sure of your vision for this girl, what her personality holds, or what her story tells. Just going by what I assume to be your original intention for the design, I would perhaps suggest some slightly more narrow eyes, or perhaps some of a broader variety. If not then perhaps tweak the left eye, it appears to be a little higher and smaller than it's right counterpart there; simple fix there though.
Now the hair seems to be rather flat, with little flow or life to it. Hair goes all the way around the head, and with a position such as this the hair would cover parts of the front and the back hair wouldn't be shown all too much.
Here is another reference sketch I have made for you:
I do hope this critique helps you out in further improving yourself, just keep working hard and never give up on your goals. If you ever need further help, feel free to note me! I will gladly help as much as I can
Keep up the great work, and I look forward to seeing more from you!