Thanks for all your advice.
I was curious to see what others would do in this situation. I notice a few scenarios.
What I will most likely do is...if this happens, I will ask my non-wj daughter if she has any objections to me hanging out with her ex, as some of you suggested, but I will wait awhile to let things cool down, first.
I really hope they can resolve their differences, as I love them both, but my allegiance of course would be to my daughter.
Thanks for all the advice, and I'd be interested to hear what more people here have to say on this subject.