Welcome to the Board. Let's cut to the chase (and as they say in Al Anon and Nar Anon, take what you like and leave the rest).
I'd appreciate any help here. I realize it is probably her reaction to early recovery, but it is unbelievably frustrating to be dating someone who is dead to the world.
Who says you have to date her? It's not like you don't have a choice in any of this. You found out 18 months ago she was doing heroin, and for 18 months, you tolerated it. Even though she's done all sorts of drugs for 15 years and has a history of alcohol abuse, you've stayed with her.
I'm less interested in her tentative steps at recovery and more interested in what you're getting out of this relationship.
If she's truly, truly serious about recovery (and time will tell on that score), I can tell you straight up she won't have the emotional bandwidth to be a committed, responsible romantic partner for quite some time.
So, if you're determined to ride this out, this is what you're signing up for. And if that's good enough for you, you may want to ask yourself why you're settling for someone that can't give you what you probably need.