how can I verify her email address if she hasn't had a gmail before

we unlocked my phone so we can put line on her phone and apple wasn't letting the phone activate it so once I came home I activated the phone with my Mac but the problem now is that I made a new Apple ID for my sister and it accepted it but its telling me. to verify. the email address which I can't or don't know how to do because she's never had an email address and now I can't access anything until verifying it. What can I do to fix it?