How to deal with an overbearing volunteer leader?

I'm part of a volunteer-run organization with an overzealous board chair.

She insisted upon calling in the middle of a workday during an especially busy week. In response, I directly set boundaries with her about emailing about what she needs to discuss and us scheduling a time from there. Her rejoinder is to ignore my professional boundary and state we need to learn how to communicate with each other.

I am genuinely confused given that we're both volunteers, the organization has no urgent programming needs, and no one else has called me in the 14 months I've been on the board.

What is the best course of action? Should I reiterate that email is the best and least intrusive way to contact me? Do I need to lay out where I place volunteering on my priority list -- below health, family and paid work?

How do you deal with an overbearing and demanding volunteer leader?