Perhaps she was hoping for a complimentary upgrade?
We don't have any idea how Anne finances her country estate and all that she owns. Maybe she is constantly trying to keep costs (which have increased quite remarkable in the last years) in a controllable range. Once you have learned to economicise, you don't stop that only because people think that being a princess means being immensely rich!
When I'm on holiday I most of the time pay extra money for sea views - but then I'm down there for a longer time and enjoy them! But to only sleep in that room?