I coach 11 year old girls, and we do TONS of dribbling drills. The best I've found is to do lots of two ball drills. This way they work on both hands at once and it really helps with overall eye-hand coordination.
Some of the best I've found include:
1. Get into almost a defensive position, legs bent, back upright, chest out. Elbows bent, strong wrists. Dribble both balls slightly to each side, making sure to use a strong dribble. Try to bounce each at the same rhythm, then switch it up so you are alternating bouncing rhythms. You can stand in front of her and hold up numbers on your hand that she has to call out, so she practices keeping her head up.
2. Practice doing five dribbles and then working in a crossover dribble in front, crossing over each ball at the same time but trying not to hit the other. If she gets good at this do behind the back.
3. Dribble one ball while trying to throw the other up with one hand and catching. This is a great way to practice keeping your eyes up.
4. Do two ball dribbling at first walking forward, then trying to go at game spped. Use the lines of the court to practice doing a stutter step and then pushing forward.
5. Use cones to practice dribbling at speed, then crossing both balls over to practice changing direction.
6. Use a blindfold to see how well she can do these drills without looking. My girls really like this!
Good luck! And search for Moriah Jefferson on youtube to show her what hard work can get her