What would you do about this?

My husband and I have been married for many years. He has a terrible family really but has always had this kind of soft spot for his mom. Anyway the relationship has been strained for many years. Lots of drama. I have come to figure out while taking a step back, observing and reflecting, my MIL is a very manipulative and abusive person. So much trauma has come to the surface for my husband since our son was born. It’s like he is reliving it now. A few years ago, it was decided that my MIL wanted to put an apartment in Europe in my husbands name. My husband’s grandma had been living there for 20+ years. She died and she was going to sign it over to him. He decided we would move in there(we were living in that European country at the time) but first completely renovate it. So we did. We put over €60,000 just in materials into that place. Not including any labor. My husband worked there everyday for over a year. We finally moved in and a year later returned to the US. We plan to go back and forth but US is primary home. So when we returned, the plan was still to sign over the apartment to my husband. But they just need to do it together. So the plan was to go at the same time together. Since then she has behaved horribly towards my husband, our son and myself. She was having huge tantrums and causing lots of drama and stress. To the point that we don’t allow interaction between her and our son. Anyway, the plan always was that we would be in a home that we maintain, but is owned by her while in US at least for short term. When we were in US, she would be in Europe using the apartment that we renovated. She went there and was supposed to make the arrangements so that my husband could fly there and sign all the paperwork to change ownership to his name. That didn’t happen. Now she is preparing to return to US, didn’t change the name and had now said she has changed her mind and plan. So we put basically €100,000 into this apartment and now she has changed her mind….I know, I know we should have had a contract. So we have now taken the stand that we will not leave the house we stay in in the US until the apartment is changed to my husband’s name. It’s a lot of money. We have tried talking. She gets defensive. She just can’t or won’t see it from our point of view. We can’t afford to just walk away from it. The court in US doesn’t have jurisdiction over the European property. The court in that country is a bit different than US and very slow. We don’t know what to do. We stay here (sort of as a protest) and have the stress of her. We walk away from her and we leave it all behind. What would you do?