@Ruth-And-Fran1 Yes you need two listings and then you link the calendars to prevent double bookings. If you use the duplicate listing function be aware that the cancellation policy will default to flexible and the booking policy to Instant Book.
Once you have two listings you can consider blocking the 1 bed listing in high season to force people to book the whole place. Blocking one listing does not link through and block the other so if you do want a rest both need to be blocked manually.