This is a difficult decision and there is no right or wrong answer. The best advice I've ever seen is Dear Abby's: "Are you better off with him or without him?"
I do want to mention that 12 step groups are definitely not for everyone. Just as with the alcoholic/addict, many people find that the religious elements of 12 step programs are simply incompatible with their world views. Some atheists can get beyond this, but others simply can't.
It's important, therefore, to know that there are sources of support that do not rely on the 12 step approach. SMART Recovery, for example, has a forum for family and friends on its website. And of course ST provides great help too. You do not need to go to Al-Anon.
OTT