BBC's Miss Marple
In the BBC 1987 adaptation of the novel, Janet Erskine is portrayed by Geraldine Newman. Janet's jealousy concerning her husband is portrayed quite faithfully.
ITV's Agatha Christie's Marple
In the ITV 2006 adaptation of the novel, Janet Erskine is portrayed by Dawn French with a totally different backstory. Here she was a singer in the "Funnybones" entertainment troupe led by her husband "Dickie" Erskine. When the troupe dissolved in the mid-1930s, the Erskines continued to live in Dillmouth. After the war, they bought over the digs of the Funnybones and appear to have turned the building into a boarding house or small hotel called "Dunlaughin". In contrast to the other adaptations, the Erskines here are a loving couple.
At the end of the last season of the "Funnybones", Janet told Dickie that she was pregnant. They later had a son George. It is later revealed at the denouement that Janet had an affair with Walter Fane and he was the real father. It was also revealed that Dickie probably knew he was not the real father (he was impotent, at least with his previous wife). This explained the fight that Dickie picked with Jackie Afflick (a member of the Funnybones) on the last day of the last season of the troupe, a fight which left Dickie with a black eye and probably an injury requiring an eye-patch. Jackie never understood the reason for the fight but Janet had just told Dickie about her pregnancy and he thought Jackie was responsible.
NHK's Anime adaptation
Janet Erskine also appears in NHK's anime adaptation of Sleeping Murder but has a smaller role. There is a scene of the Erskines at Hillside for tea with the Hallidays and another of her watching her husband with Helen. She does not appear to have many lines. Richard Erskine tells Gwenda that Janet saw him on the beach with Helen (on the day of her disappearance). She got jealous and insisted that they leave Dillmouth, which they did the next day. Janet does not appear when Gwenda and Mabel call on Richard in Northumberland. The voice actress behind the character of Janet is not credited.