mac mini mail

In setting up my new Mac mini 2020 from iCloud I ran into a mail problem in my wife's user account. In system preferences - Internet Accounts it shows her gmail address associated with the Game Center only, not for email. I tried adding her gmail account for email but it says that this account is already in use. I also tried deleting the associated Game Center account but still got the already in use from gmail. I also tried adding it from the mail app. Appreciate any suggestions.