In the short story The Sunningdale Mystery, Mrs Sessle is the wife of Captain Sessle. She was away visiting someone during the time that all the events leading up to the death of her husband took place and could therefore play no part in resolving the mystery. From all accounts she and her husband were a loving couple and popular in the neighbourhood.
In investigating the case, Tommy and Tuppence considered whether Mrs Sessle could the mysterious lady in brown who met Sessle at the golf course and who was believed to be connected with his death. Given that there was a suggestion that Sessle was seeing another woman, Doris Evans, Tuppence said that she would naturally suspect an angered wife. However they ruled this possibiilty out because Mrs Sessle was short, whereas the woman in brown was described by multiple witnesses as being very tall.
In LWT's 1983 TV adaptation of The Sunningdale Mystery, Mrs Sessle is mentioned several times but never seen on screen.