actually we called the grandma(1), and grandpas (2) and to make a difference
it was "Tata" and "Yeyo".

i think you should only call her that IF you feel comfortable with it, if not, call her what you want, you can“t be imposed to doing it a certain way, if i were "forced" to call my MIL mom i wouldn“t no way jose!!, so i think is the same but with different people. but do as you feel better