floral prints animal prints funky shades cool,thick belts capri shorts (the kind that stop slightly above the knee) bold/neutral colored sandals/flip flops cute skirts or dresses hair bows (the bow tie kind or the flower kind)
As a suggestion, it might be best to leave the answer to that question up to the 9-year old. What's "in style" might not be something that appeals to her, and wearing it just to be "stylish" could put a lot of pressure on her.
If you're just looking to buy something as a gift for a particular 9-year old, then I suggest doing the same as you would with a gift for an adult: Get something based on what you know she likes. (eg: horses, sci-fi, country/western, flowers, etc.)