It's a little unclear what you're describing. Your wife is the owner of her old phone. She logged into it using your Apple ID. I'm not aware of a Contacts app field that indicates ownership of a device. Can you provide more details or post a screenshot of what you feel is the issue?
It's hard to say what might have caused it, but maybe her old phone had not been completely erased and set up as new. You can delete that contact and create a new My Card though if that's your intent.The "My Card" shows my wife's name instead of mine when viewing the "contacts list"
My wife recently logged into her old iphone with my icloud, and now my iphone's contact list...
It's hard to say what might have caused it, but maybe her old phone had not been completely erased and set up as new. You can delete that contact and create a new My Card though if that's your intent.
Add or edit your contact info and photo on iPhone
In Contacts on iPhone, add your information to your contact card.support.apple.com