Try recovery mode, see half-way down this page : Forgot passcode for your iPhone, iPad, or iPod touch, or your device is disabled - Apple Support
If she had Settings > iCloud > Find My iPad enabled on it then she will need to remember or find the id that she was using in iCloud to be able to then reactivate the iPad. If she can't remember it : How to find your Apple ID - Apple Support
If she can find the id then to reset its password : http://iforgot.apple.com
If she can't find it via that then she can try going to an Apple store or contacting iTunes Support online and see if they can remove the iPad from her account - they are likely to want to see proof of ownership e.g. original receipt with serial number on it before they might help.
If she didn't have Find My iPad enabled then it shouldn't be tied to an account and need reactivating.