Kat's advice is spot on. To that which she has mentioned, I'll add: Shoot at her eye level rather that up at her; find a plain background, a medium or darker tone to contrast her hair and skin, crop more tightly on her head and shoulders, and avoid cropping little bits of body parts (in this case the upper portion of her left arm). Bold crops are fine, provided they don't bisect a joint, but little bits tend to give the impression of careless composition.

Looking forward to the Mk II version!