I'm not being agressive or pedantic. I'm simply trying to acertain what exactly you did, so we can understand what is happening and be able to help you. If you want us to help you, then we need to know what exactly happened to cause this.
Asking questons and trying to determine what you did is not being pedantic nor aggressive. Its simply trying to figure out what it is you did so we understand why it would be asking for the password to an email you no longer have. Again, since you've provided no details as to where or when its asking for this we have no idea. We are not mind readers. We cannot see what you see on your devices. So we have no clue what is actually going on unless you tell us.
Its very simple, Its rare when there's a confusion by the system regarding which Apple ID was being used. In most cases, the issues stem from something the user did, or failed to do.
When is it asking for the password exactly? When she gets to what step exactly?
Remember we are not Apple support, we are just other users of Apple products volunteering our time trying to help you out.