Dona't mix business with Love is the lesson that should be learned from this. She should not have had access to his coorporation. Also, as soon as she became extranged, he should have moved quickly to have her and her family removed from having access to his assets. Still, the better path is to never give them access in the first place. Parcel out what they need and desire, never give them the keys.
Those of you who eventually make a lot of money, learn from this. Keep this in the back of your mind and protect your assets from everyone, including the ones you Love. So no on the GMB, but yes on the CYA.