iPad locked unable to unlock not enough storage on iCloud , cannot get into settings to manage.

MY wife's iPad is in lockdown, it will not allow you to unlock or even power off, a message appears on the screen saying Not Enough Storage this iPad cannot be backed up because there is not enough storage available in iCloud . You can manage your storage in Settings. There are two buttons, one is Close the other is Settings. Neither of the buttons will respond, the iPad then closes. Can anybody HELP.