Disabling Mail from receiving Gmail

My mom is having issues with Mail that she can't solve on her own, and I can't solve those issues over the phone for her, as she calls me to solve all her computer crises. She uses Gmail exclusively for her email, but for some reason the system is forcing her to authorize the Mail app to use the account, and she has no interest in using the app at all; she is perfectly happy to use Chrome to access her Gmail account, and wants nothing to do with Mail. I tried to disable the link between the two in Internet Accounts, but that seems not to have worked, as the system is still butting in with demands for authorization. How do I disable Mail from accessing her Gmail account permanently, so that these messages cease?