Hi adviceisnice
If you have doubts, and it sounds like you do, I think you'd be justified in holding a firm line. For what it's worth I don't think active addiction is ever a reasonable excuse for behaviour you find unacceptable.
Have you seen our Family and Friends forum? I think you'll get a very valuable point of view down there too, from people who've been in similar situations.
Friends and Family of Substance Abusers - SoberRecovery : Alcoholism Drug Addiction Help and Information
Welcome to SR
D