While this is a great "on the surface" example to make with some very good points or lessons to be learned from this, I feel it's important to point out the obvious here.

They have been together for over 12 years. The punitive way Musk handled this was clearly not motivated by purely business events. I have no inside info re their relationship, but I do know most marriages (mine for instance) don't last 12 years. Living on top of someone that long will create deeply ingrained resentments. Just a guess, but I bet some of that may have manifested itself in this situation which also makes it a terrible example for any normal negotiations.

Let's face it, she waited 12 years to seek appropriate compensation? He didn't elevate her for 12 years, yet she was "key to his success"? Allow me to break the foundation to all this with a jackhammer.