How to change iCloud user email address

You need to see the articles iCloud: About your @icloud.com, @me.com and @mac.com email addresses - Apple Support

About your Apple ID email addresses - Apple Support

Delete an additional email address

1. Sign in to appleid.apple.com.
2. Select Personal Information, then select Email & Phone Numbers.
3. To delete one of your additional email addresses, click the Remove button  next to the address.

How exactly did the secretary do this?

Where are you seeing this address exactly?

There is no way to add a email address to iCloud, unless you are saying she logged in with your husbands account on your device.

You need to explain exactly what happened and where you are seeing this address before anyone can advise.