Hi Meaney123,
Welcome to Apple Support Communities.
It sounds like your niece may have put a passcode on her iPad and it's now disabled. The iPad can be restored from backup using the computer it last synced with or you can restore it from recovery mode using a computer with iTunes, as outlined in the article below.
iOS: Forgot passcode or device disabled
http://support.apple.com/kb/ht1212
I hope this helps.
-Jason