@Monika64 this is one I would push off onto CS. Call & say “ this is a third party booking, but I am happy to host IF you get the actual guest to create an account. “
CS has the ability to call guest one, call guest 2 and transfer the reservation from one to two. You can’t do any of that. So set a deadline that you’re comfortable with and get CS working on it. Very doable.
If they don’t get it done then you go back & insist on cancellation.
& best I can tell, anyone can pay for anyone. So if guest two gets a profile guest one still can pay.