Change in Vacation Policy

My mom has worked for Aramark for the past 7 years. When she first started working there, the policy was that after 3 years she would earn 15 days of vacation per year and after 7 it was 20. The employee handbook was revised in January of 2002 and the policy changed to after 2 years it's two weeks and after 8 years it's 3 weeks.
Does this mean she is under the new policy? or old? She has been unable to get a straight answer from anyone!!!!! She feels she is entitled to 15 days and now it would be 20.
Who can she contact about this???!!! (her manager is of no help and can be awfully rude)