Dear Abby: Between competing grandmas, perfect nickname is earned through memories, not marketing

Dear Abby: My grandson is 2 and has started to call me “Mimi.” The problem is that his other grandmother chose Mimi for herself. My daughter-in-law is annoyed and does not want him calling me Mimi. She also doesn’t want me to be called Mom-Mom because he calls her Ma-Ma. Am I wrong to be upset?