I do this to be kind, okay? I promise you if I didn't think the drawing was that great, I'd say, "Wow, pretty good!" and leave it at that. Because you obviously have talent, I want to encourage you to improve.
Like people have said, the feet aren't right. Firstly, they shouldn't be facing the same direction. Stand up, get comfortable, and look at your feet. Often drawing them at roughly a 40 degree angle to each other. In a 45 degree angle picture like that, I would leave the right foot and put the left foot in a direction more or less facing "us".
The feet aren't sitting right. They're tilted down too much. She's either standing tippy toes or her feet are flat, but what you have is a little inbetween. Try to make them flatter (ie. put the toes up)
The pants... obviously, they're supposed to be short. They don't have to be cutting off the circulation in her... *ahem*. Trust me, even on the tightest of jeans, there's a little 'give' between the legs so I'd suggest just putting a little er, bit of extra material in there. Also, the zip area should have a few wrinkles across it. A fat tummy will fill that part in nicely but she's got a pretty darn flat stomach so it would look a little more natural if you made the material look a tad .. well, not looser, but it should at least have some "taught" lines.
This is something EVERYONE has trouble with at some point, it was always one of my biggest problems. The hand on the hip. It's tempting to draw it like that because we know it's curved but put your hand on your hip and you'll notice how unnatural it is to have the hand raised and curved like that. It's also hard to keep the pinky sticking out like that. The arm also looks rather unnatural. Take care with tapering the arm too much at the wrist, and where the wrist seemingly joins onto the hand. One of the best techniues I ever learned was not drawing the elbow like a straight corner. One side of the elbox is strait, the other side has more of a curve. Best to just look at other drawings to get a sense of how this works.
The left arm... the upper portion is too long. Compare the length from the shoulder to the elbow in both arms. It's extremely, EXTREMELY difficult to draw the arm/hand in that position. Again, my best advice is to straiht out copy professional pictures that use that pose to get a good sense for how to use it.
The face shape is okay. Obviously there's no rule on how the face shape should be, it depends on your style. For such a 'flat' shape like that though, the facial features shouldn't be quite so rounded. Notice how you can't make out the cheeks or shape of the nose? Even if you do't draw those things (I don't), it's good to organise the prominant facial features in such a way as we can see they fit in with the actual shape of the face. Try to keep the eyes level, for example, and the nose in the centre of the fae, and the mouth right (in the context of the character, obviously not physically on the picture).
The hat ... is perfect, really. You didn't fall into the trap of not giving it enough shape. It's very nice. I'm also most impressed with the legs. Fantastic shape! You put the navel in the right place, as well.
Another thing I would recommend you think of is making the pose a little more naural, or dynamic (either way). Those inbetween poses are so tempting and of course, are great when you're learning how to get the body shape right. For an actual picture though, it always ends up looking a tad awkward.
(I hate the G-string, but that's me. I don't find G-strings sticking out of pants attractive at all).
EDIT: Oh yeah, I forgot the mention, your colouring is great!
