Ditto to everyone above... alcohol is a drug, and if he has attended even one NA meeting then he knows that because that axiom is included in the preamble of every NA meeting. It does not matter what his original DOC is - if he drank, then that is a relapse.
Have you considered taking your daughter to a couple of meetings of Al-Anon or Nar-Anon? It would help her learn a little about the disease of addiction and possibly she will not enable him in such a way in the future.