Henrietta's Sister, known as "No. 7" or Irene, is a Wisbech and Upwell bogie coach, currently preserved by the Midland and Great Northern Joint Railway Society. In an annual, she was described as being Henrietta's only surviving sister, with a noticeable different of being a bogie coach whereas Henrietta is a 4-wheeled coach. In the television series however, Henrietta also has a sister by the name of Hannah.
From the beginning, the Wisbech and Upwell used its own special passenger stock. Initially, only four wheelers were used, but bogie coaches were introduced in 1884. The coaches had balconies at each end and a drawbridge type gangway between coaches. Each balcony had an emergency hand-brake wheel. The coaches looked squat and low-lying due to the need to handle raised track and the absence of platforms at some of the depots. All the four-wheeled coaches were scrapped by 1948, but the bogie coaches survived into British Railways.