GALVESTON — A jury sentenced Cheretta Smith, 20, to 84 years in prison on Friday. Smith pleaded guilty to murder in the Feb. 12, 2010, slaying of her grandmother, Theretta Gayden Miller, 57, who was found dead in the Texas City home she shared with Smith. Smith admitted to stabbing her grandmother twice, although prosecutors say she hit her grandmother on the head with a candleholder three times and stabbed her four times in the stomach.