I advocated spending time with her father and her husband. Were it a man, I would advocate the same thing - spend some time with his mother and his wife.
The situation described in the OP was her father was in town, which wasn't usual and she wouldn't ordinarily get the chance to spend time with her father on Father's Day. So for her husband to be pissy about her wanting to share one meal with her father was totally not on, as far as I'm concerned. And if my hypothetical husband wanted to spend part of Mother's Day with his mother, I wouldn't be bothered at all, as long as we got to spend part of the day together. Bonus for me if he took any hypothetical children with him to visit MIL - I'd get some time to myself for a nice bath or whatever else I wanted to do.