Is it possible to get out of an LLC contract due to problems with the partners? What are the steps to get out if it is before the "expiration date"?

I am asking for my fiance, so I may not have all the best details: He bought a small restaurant with his partner, who is turning out to be crazy- causing issues with the staff, having emotional/raging outbursts over personal issues with him, threatening to damage his motorcycle...The restaurant has been open a little over a year, and just making it financially. They have a large bank loan in addition to the investors. He wants to leave the business because he its very unhealthy to have this kind of relationship with the partner, but has an LLC contract (I would believe with her and the investors?) Is he able to get out of it with her threatening injury or some kind of breach by the way she has been acting? What financial responsibilities would he have if he can get out? This woman is very crazy, she may let him out to try to salvage something with him..do the circumstances change if she mutually lets him out? ANY information is greatly appreciated. Thank you.