Permanently blocked from authorizing Digital Editions on iPad

I tried to create an authorization ID for a Digital Editions installation on my iPad for my daughter - the books are hers, and I thought it was a good idea for her to manage her own reading account. However, it turns out she's too young for her own account.

This would be fine if I could then change the authorization to be for me instead, but the app totally refuses to ever allow me to re-authorize the account. I've uninstalled and re-installed it several times, restarted the iPad etc etc. Done everything I can to wipe the failed attempt, but trying to authorize some other way simply leads me to an 'Access Denied' page on Adobe's website.

There should be some way to reset the app authorization - it's absolutely unacceptable that my daughter is locked out of her DRM books by this awful application.