Typically an Apple ID is an email address you have used. If you are currently using a mobile device that is logged into your account, go to Settings and tap your name at the top.
Look in Keychain, and in a browser's security settings if you use it to automatically sign into Apple when using a browser.
This support article describes ways to find your Apple ID --> If you forgot your Apple ID - Apple Support
or go directly to this link --> https://iforgot.apple.com/appleid
If you still need help:
Contact Apple for help with Apple ID account security "This article provides country-specific Apple Support contact information for customers seeking help with their Apple ID password or other security-related issues."
Contact Apple for support and service - Apple Support
You didn't have to have her sign out, BTW.
Read this support article to find out how to use the Find My app to locate a missing device or item. Click here --> Find your lost Apple device or AirTag with Find My - Apple Support
- A person can use the Find My app on a device owned by someone in their Family Sharing group.
- Alternatively, anybody can sign into https://www.icloud.com/find to locate their device using a browser. You don't need a two-factor code if you use any internet browser and log into www.icloud.com/find
Note that the address must include the "/find" as shown above.