It is illegal it doesn't matter if she is 18 or not in ALL US States to give a minor alcohol. For that HE can go to jail .. my STBX has major issues with drinking all documented .. his ass in jail end.of.story. I DO NOT play when it comes to drugs and alcohol .. for a parent to physically harm a child (you will need a definition of child I do believe that the fact she's an underage drinker trumps this issue)the reality is NO alcohol .. period. The idea that he is setting his daughter up to have issues with alcohol is a big red flag .. some education for her about the life long effects of addiction on her body (especially as a cancer survivor) it sounds like there are other issues going on. Good luck and big hugs .. this is a tough situation.