Can my wife's iphone be used as a trusted device?

No. trusted devices are devices logged into your Apple ID, and are different things from trusted phone numbers.

Your wife’s iphone should not be logged in to your Apple ID for any reason whatsoever.

You can set your wife’s phone number as a trusted phone number to receive Sms messages or voice calls with the 2 factor authentication codes, but this is different to being a trusted device. They should not be confused.

If your wife’s number is set as a trusted phone number, you can then manually request a code be sent to it. It will not automatically receive codes like trusted devices would.

What is a trusted device?

A trusted device is an iPhone, iPad, iPod touch, Apple Watch, or Mac that you've already signed in to using two-factor authentication. It's a device that we know is yours and that can be used to verify your identity by displaying a verification code from Apple when you sign in on a different device or browser.

Yes, if it is using the same Apple ID that you are using. Otherwise, you can have your wife's phone receive messages with authorization codes. Post back if you need more help setting this up.

Yes you can. Go to Settings > [your name] > Password & Security and tap Edit next to Trusted Phone Numbers.

Here is the support article (relevant section toward the bottom):

Two-factor authentication for Apple ID - Apple Support

Not as a trusted device, but as trusted phone. And you can also add her as a Recovery Contact→Set up an account recovery contact - Apple Support

frustrated-mike wrote:

Can my wife's iphone be used as a trusted device?

As an alternative to the above discussion, here is how to: Set up an account recovery contact - Apple Support

This Account Recovery Contact allows you to regain access to your Apple ID, without compromising its security.

You explained very well the difference from a Trusted Device and Trusted Phone Number.

Thanks for that added info.

Mac Jim ID wrote:

You explained very well the difference from a Trusted Device and Trusted Phone Number.

Thanks for that added info.

Thanks. 😉