Simenthcone tablets are one way to help.
It is over the counter, however, you must tell your friend that they have to get permission from their doctor or Et Nurse before trying anything. Simethecone is also one of the ingredients in Mylanta. Have your friend mention these products to their doctor, before trying. The gas will lessen as the body gets accustomed to the changes from the surgery. A Nutritionist can offer suggestions on what foods cause excessive gas.