ipad Activation Lock

My mother-in-law passed away recently and my wife is trying to unlock her iPad but the activation lock is on. We don't know her details to unlock it and she doesn't have an iPhone to delete the device from her Devices List. We have managed to access her Apple ID account but cannot access the iPad and the device is not showing in the list.

Not quite sure if it is an iPad 5th gen but I had to pick a version.

Any ideas.

Thanks in advance.