In Gmail make sure you have the account set up to "send as" whatever the email address is for your wife, and go through the setup process even if you never intend to "send as" from the Gmail account. That usually cures the problem, if I understand it correctly.
For example, I set up Gmail to "send as"
YYYY@domain.com. As part of the setup process Gmail will send a message to that address and you have to answer to show that you really are at the address. After that, Gmail will usually successfully accept email forwarded from
YYYY@domain.com.
https://support.google.com/mail/answer/22370?hl=en