At age 9 very few balls are hit to the OF with a chance of an out. Put her at 2nd, SS or 3rd if she has the arm. If she has the best glove put her at first. That is where most of your outs will be made.
Very fine advice.
If you want her to get plays, and she's 9 - answer is infield.
Often we coaches put small girls at 2B. The throw from 3B to 1B is very hard for 9 year olds.
However...
You gotta get them reps at multiple positions. That's really your job as coach. Yes, they can have a primary position but please rotate girls, give them all chances. I fear you're walking on a straight path to DaddyBall Town, and that won't go well for you, your team or your daughter.