Hi Dhoffman1982 -
At this time, the Xfinity Home mobile app only supports sign in with the one email address associated with the home security account. You can sign in with your wife's email address or I can open a ticket to have the email address updated to another email the both of you can use.
I've added your account to a ticket that is already addressing the issue that you are experiencing. Our engineers are actively working on a fix & I will follow up with you here.