Catherine Greig, the girlfriend of notorious Boston gangster James (Whitey) Bulger, has agreed to plead guilty to charges she helped him escape — but she won’t have to rat out her man. The feds nabbed Greig, 60, along with her mobster lover after they had evaded the law together for almost 17 years. A plea agreement filed Monday, first reported by the Boston Globe, stipulates that she won’t have to testify against him. “In early 1995, I agreed to join Bulger and travel with [him] during his flight from law enforcement,” she wrote in the agreement. She could face five years in federal prison on charges of harboring a fugitive, identity theft and conspiracy. Bulger, who went on the lam in 1995 after his FBI handler tipped him off to a pending racketeering indictment, accused of 19 counts of murder and a host of other crimes.