JOLIET, Ill. — The girlfriend of a man authorities say killed eight people in an afternoon rampage in Joliet last month will plead not guilty to three counts of obstruction of justice in Will County, her attorney said Thursday. Kyleigh Cleveland-Singleton, 21, shares a 3-year-old son with massacre suspect Romeo Nance, 23. Nance died Jan. 22 of a self-inflicted gunshot wound during a standoff with law enforcement in Texas. The day before, authorities believe he shot seven of his relatives and an eighth, unrelated man to death. Cleveland-Singleton faces obstruction of justice charges for alleged…