This must be very stressful, worrying about what this could do to your parents.
Just because she's saber-rattling about refinancing doesn't mean she gets her way. This is a complex legal issue - forced house sale, whether or not she waived her right to the 25% equity, etc.
Also... how the heck did she not consider her equity in this house during the D settlement? Crazy...
I guess first you need to determine whether or not she has a legal basis for her claim. If she does then you unfortunately probably have to deal with it at some point. (No judge would order an immediate sale in 30 days, that is nuts).
One thing I notice is you seem to be reacting to your W's black/white offer... buy her out and refinance or bust. The reality is there are likely many options to resolve the issue if she does deserve (legally speaking) all or some of her share of the equity. Perhaps even a good private mediator specializing in this issue would be able to help in a much more cost-effective way.
Regarding the bigger issue of your XW revisiting things... I think this happens often. I fully expect it to happen in my situation.
One friend of mine had an amicable D several years ago. He had his kids 3 weekends a month. Once his XW stopped receiving support, she filed for 100% custody, claimed abuse, and he spent 6 figures clearing his name. He now has 50-50 custody but constantly worries that she may come back with a new claim and drag him back to court.
Another acquaintance of mine, for 15 years, knew that every September his XW was going to file a move-away request or something else that the court would not grant, but would require him to spend legal money and fight.
She won't change her behavior until her narrative changes. It may never change. Maybe she's in love with the fight. You can choose your own rules of engagement, including whether to ignore.
