A Union County woman was killed Thursday in a head-on crash, according to the South Carolina Highway Patrol.Union County Coroner William Holcombe identified the woman as Barbara leMaster McKinney, 79, of Buffalo.The crash was reported just before 1 p.m. on Highway 215, or Buffalo West Springs Highway near Fairforest Heights, troopers said.McKinney was heading north in a 2007 Pontiac 4-door sedan when she was hit