A Dangerous Woman (1994)

Martha Horgan (Debra Winger) is a withdrawn, mentally disabled woman who lives with her aunt, Frances (Barbara Hershey). One of Martha's unusual traits is that she doesn't lie, a quality that leads to her getting fired from a dry-cleaning shop thanks to the actions of the shifty Getso (David Strathairn). Conflict seems to follow Martha, since she also becomes romantically involved with local fix-it man, Mackey (Gabriel Byrne), who is sleeping with Frances as well.