How do I sync the Google calendar of two separate Google accounts?

My mother and I have two separate Google accounts and two separate Androids. I’m getting tired of having to go through the weekly ritual of manually syncing our calendars by reading events out loud. How do I sync the two calendars together, so that when we add events on our calendar, they appear on the other one?

Have you tried adding her calendar to yours? I think she needs to make it shareable.

See here

My wife and I have a shared calendar and add anything that is relevant to us both to that one.

This, but you would also probably want her to add your calendar as well. Then you both choose to display your calendar, the other persons, or both at the same time. You can choose what colors each person’s events appear in if desired.