I call my MIL Mamma Pat or Pat or Grandma depending on the situation or my mood! I think she is fine with all of them as long as it isn't one of her kids calling her by her first name! Watch out! She took DH aside and told him he was welcome to call her Mom, Mother, or Mommy, but he was still her son and she was still his mother and he would NOT EVER call her Pat. I could call her Pat, but not him! He hasn't since!