At the beginning of the month we had great visits from both sets of Grandparents. Grandma and Grandpa M were here first and the whole weekend M3 insisted on using their last name when talking to them. It was Grandma M____ and Grandpa M_____ all of the time. Grandma tried to tell her that she could just use "Grandma," but M3 wouldn't budge.
My parents came a few days later and M3 insisted on calling them Grandma and Grandpa M____ too! After the first day she'd say, "Grandma M____, no Grandma B..." By the end of their trip she had it down most of the time, but she wouldn't just shorten it to Grandma or Grandpa.
This weekend she started calling me Mama M_____. Today she used an 8 word sentence, "Mama M____, I have mama milk soon please?" But, this better be a short phase.