Hi, Abeula, and welcome to the forum. You have quite a situation there. How much you should or want to get involved is really up to you. First of all, you need to make sure that your niece understands that her b.f. has hep C and that is a disease that doesn't just "go away" without treatment. Was there any mention of treatment? I would think that the VA would do that much. Not sure about transplant. As far as Medicare Part B, the b.f. could most likely get Medicaid to pay for it. They pay my monthly premium. If he doesn't have Part D (prescription drug plan), he can get that when there is open enrollment and Medicaid would also probably pay for his premium for that. On the Medicare site, it's known as "extra help" in paying premiums.
If the b.f. is still drinking, he would not even be considered for a transplant. He would need to be verifiably sober at an approved program (AA or alcohol counseling, depending on what the transplant center requires) for 6 mos. before he would even be evaluated! He needs to stop drinking now. He should also get a referral to a Transplant Center where he can get further information on their requirements (they vary from center to center and even state to state.) Medicare does pay for transplants, I think.
The medication he was put on for high ammonia was most likely Lactulose. This is to prevent encephalopathy. Between that and the draining, I would say that he is end stage. That doesn't mean that he's going to die tomorrow, but that his liver is in serious trouble. You might try to explain this to your niece and also tell her that she needs to get on a waiting list for suitable living quarters in case something should happen to her b.f. He is probably going to be in and out of the hospital for paracentesis (draining of fluid in the belly) and perhaps some emergencies such as bleeding varices. This is just the beginning of a long road. You might want to recommend to her that she contact his family and let them know that he is very sick. Unless it becomes a necessity, I don't think you should be the one to do this.
Hope this helps a little. Keep us posted on the situation.