Flaffy
I've tried changing the email on that account already. It doesn't let me, tried both on mobile app, mobile safari, and laptop chrome.
This account was used with Google's sign in button. The other account was made with an email from a referral from me. Not google sign in.
And no, they do not have my password thank you very much for worrying, I accepted it on my email when they created the account. They had forgotten their email then (don't use it often) so I offered to let them use mine for the time being, both thinking that we could just change it whenever they remembered/found there's, or that you could delete the account. Which seems to not be the case, hence why I asked.
The disallowing thing wouldn't do anything, as this account is with Google sign in using my personal email, and that other account is using the same email just not google sign in. On the contrary, it would kick me (this account) out, I'd loose everything on here which is not what I want. They no longer use that account and have told me "just do whatever with it".