@Roberta121 You have a lovely studio! As you say, you have been obliged to list it as a Private Room now. All I can suggest is to list the accommodation giving the Base Price for one person, and then add the extra for the second person in the Pricing section. This way, at least your accommodation will appear in a search for Private Rooms when the guests select a lower price. Hopefully, they will then see that it is a beautiful, virtually self-contained studio and will be won over, and will recognise that the second guest fee is justified.
You could also try increasing the 5% reduction for a week's stay.