Mary-Beth has married at least six times, and her marriages have ended with her husbands dying gruesome deaths; with her taking part in most, if not all. She wears either pants or dresses, as she mentions wearing them interchangeably as well as mentioning the fact that she wears bloomers. She also has numerous children and broadcasts from Bone County, which is a desert region near Las Venturas. Mrs. Maybell is never seen in person, only heard on the radio. Sometimes, Mary-Beth puts a harmonica in her pants to make music, a talent she learned while in a women's prison. It is likely that Mary-Beth ended up in prison from killing one of her many husbands.
It is hinted at that one of Mary-Beth's marriages was to K-DST DJ Tommy Smith. Just before the song "Strutter", Tommy will sometimes remark, "This song will put hair on your chest. Sure did in my ex-wife's case". Mary-Beth repeats the exact phrase about a song on K-Rose, only she says it put hair on her chest.
During the course of her frequent marriages, she managed to give birth to 9 children, which some of them are going through puberty (Mary-Beth mentions one of them going through a "natural transition to womanhood"). The weirdest of her stories about her children came when Mary Ellen (probably the oldest of the 9 children) was born on a pool table and the players kept on playing. Mary-Beth is also said to be heavy-set, which she reveals after Juice Newton's "Queen of Hearts" song. Mary-Beth's surname may come from Mother Maybell of the Carter Family, although she implies this may not be her real surname.
Mary-Beth appears to be concerned about the gang situation in Los Santos as at one point early in the game she can be heard asking why the different gangs can't just get along.
Mary-Beth is voiced by Riette Burdick.