What do we know of Mindy's mother? She has a father, but where is her mother?

I dont know why they did not talk about Mindy Mother on Mork and Mindy.

I never thought about that before--but you're right. I can't recall any mention
of Mindy's mother on the series.

Mindy's mother died when she was young, there was an episode that featured that event, the one where Fred brought home his new wife, an episode entitled "A Mommy For Mindy" in season 2.