Okie, since I'm your sister and I know you'll still love me afterwards...

Her neck is coming out of her left shoulder. The neck itself looks fine. The headshape doesn't look right (the circle tool is not your friend), mostly because of the way the nose is, there needs to be more definition between her lips and nose or summing. Her arm is forming a j shape (I don't think arms bend that way), and the whole anatomy of the abdomen is slightly off.

Don't draw the clothes she's wearing, draw the clothes over her body, do you understand what I mean? Think about where a persons joints are, where the waist ACTUALLY is, not where you think it might be, and think about how people would actually move.

Then there's the coloring, and bah, what a crap job, I know you well enough to know you can do better. What the heck kind of hair is that, it looks like a floppy hat. lol. Think about where the light is coming from, think about where the light would not reach, think about which parts of the body are round and which are flat.

Other than that, I have to say my favorite part of this picture is the background color. Red is always a plus. *thumbs up* ^_^