Forgot Id but know know the the password

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

Read this support article about what to do if a iPhone or iPad is lost or stolen -->

If your iPhone or iPad is lost or stolen - Apple Support

The same information applies to her. I just said "you" because I answer this question a dozen times per day here and have a prepared reply with "you".

Remember the people here are just Apple product users like yourself. There is nothing we can do other than provide you with suggestions of things you need to try yourself.