Pop Pop

We call my father-in-law and mother-in-law Pop Pop and Mom Mom, respectively. This is what their first grandchild called them so it has stuck. My daughter signs Pop Pop. She says Pop Pop. Does she sign or say Mommy? No. Does she say Daddy? Of course (although not as much now that she has learned to say Pop Pop). I don't know why this bothers me so much, but it does seem to bother me greatly. I guess I feel like she should say mommy first since I am the one who is with her most of the time. I guess I feel like she likes Pop Pop (and Daddy) better than me since she will say their names. Talk about feeling like an "invisible mom!"