Granddaughter can't remember ID that she used on my iPad

I let my teenaged granddaughter borrow my old iPad 2 last summer when she was staying with us. I set it up as a new device and she signed in with an Apple ID that she set up just for this iPad. One year later I want to give the iPad away to someone who cannot afford one and it indicates an activation lock associated with the Apple ID that she set up and used last summer. The problem is that she cannot remember the ID and password. We could of course reset the password if we only could remember the ID but we/she have tried everything that she could come up with as a possibility. Is this iPad permanently bricked or is there some workaround that the folks at the Apple Store maybe could help me and her with to get it un-bricked? Any advice is appreciated.