A former human resources manager arrested after a massive immigration raid at an Iowa kosher slaughterhouse has pleaded guilty to federal immigration charges. On Monday, Elizabeth Billmeyer pleaded guilty to one count of conspiracy to harbor undocumented aliens for profit and one count of knowingly accepting false resident alien cards. The 48-year-old Billmeyer worked at the Agriprocessors Inc. plant in Iowa. She faces up to 20 years in prison and a $500,000 fine. She remains free on bond. Her sentencing date has not been set. Federal agents arrested 389 people during a raid at the plant last May.