Hello, Barb, and welcome to the forum. I'm sorry to hear that your sister has liver disease. From everything that's ever been posted here regarding transplants, my impression is that 6 mos. of documented attendance at AA or authorized alcohol counseling are the requirements for evaluation for liver transplant. Being listed depends on the MELD score.
Hoping, that's great news that your dad is doing so much better. I think you can attribute that to his lack of alcohol intake. That is the single most beneficial thing that anyone with liver disease can do. If his liver disease was caused by alcohol overindulgence, then it's very possible that he can recover from the damage if he continues not to drink and also to watch his diet and follow up with his hepatologist and all the meds and requirements. Do be aware, though, that his status could suddenly change for no apparent reason. He will just have to be monitored closely and encouraged to stay free of alcohol and to live a healthy lifestyle.
Do keep us posted.