Help find stolen iPhone

She can use any internet browser and log into www.icloud.com/find

Also see: If your iPhone, iPad, or iPod touch is lost or stolen - Apple Support and If Find My iPhone or Find My iPad isn't enabled on your missing device - Apple Support including the following:

If your missing device doesn't appear in the Find My app or at iCloud.com/find, you didn't turn on Find My. There's no other Apple service that can find, track, or flag your device for you. But there are steps that you can take to help protect your data.

Are you accessing the website using www.icloud.com/find ? That should not need a two-factor verification.

If that's not working and if there are no other trusted telephone numbers configured, then you will likely need to contact Apple, and may need to recover access to the Apple ID.

Links to more info:

How to use account recovery when you can’t reset your Apple ID password - Apple Support

Contact Apple for help with Apple ID account security - Apple Support

See the following from my previous post:

She can use any internet browser and log into www.icloud.com/find

Note the "/find" in that link. No two-factor authorization code is needed when logging in with "/find."

Yes, but you did not follow the instructions. If you use this EXACT URL→https://icloud.com/find <—CLICK ON IT IN THIS POST

you will not be prompted for 2 factor authentication

If you use https://icloud.com without added /find on the end you WILL be challenged for 2 FA.

You can’t track it if it’s offline.

Beware of a common phishing scam: You may get a text or email from “Apple” or “Apple Security” saying your phone has been found and to click on a link to see its location. This is NEVER from Apple; it is from the thief or fence to steal your Apple ID and identity. Delete any such message without responding to it.