Open the App Store on the iPad and choose the Purchased icon from the bottom. You should be able to download the app from there. If you don't have a purchased options (some countries don't yet), then just search for the app and reinstall it. You will not be charged again.
Unfortunately her progress will gone. But, if you've done a recent backup before it was deleted you can try restore from backup in iTunes. Just make sure other games/documents or other stuff that has been recently changed isn't more important, because they will be restored to their previous states also.