Hi. My friend has a problem. She gave access to someone to take care of her account till She can buy..

Hi. My friend has a problem. She gave access to someone to take care of her account till She can buy a new phone. That person linked the game account to his Google account but we managed to get it back and re-link to her's. But it turns out either that person gave access to someone else too or he logged in from another device too because someone still keep logging into her account. There's no other device linked to her Google account so it must have stayed logged in from the previous Google account. She created a ticket and did gave the GM the receipt from the first purchase confirming its her account and asked to remove any other devices except her's. She got no help till now. The question is : is there any method for her to remove that device?