.... the show, i.e. a story reason in an episode or was it that she was there in the last ep. of the second to last season and she was gone the first episode of the last season (the girlfriends season)?
shareIn the first episode of the last season it is mentioned that she died in a plane crash.
shareApparently it's 8 months after the plane crash and Mac is already dating.
It is all explained in an off-handed comment by Enright. They don't really explain about Mildred being replaced by her sister.
Season Six Episode 3
Agatha mentions to 'Mrs. Partridge' that her sister came into some Money and moved Back East.