Welcome to SR, though sorry for what has brought you here.
My stepmother is addicted to a lot of meds, ativan being one of them and it's in the same class of meds (benzo) as xanax. She also has the memory loss issue.
I hope you check out the forum Least linked to. Unfortunately, if your parents don't see it as a problem, they're very unlikely to do anything about it.
I'm both a recovering addict and a recovering codependent with loved ones who are still addicted. I always thought I could "get it through their heads" and that just doesn't work. Thanks to the great people on the Friends & Family forum, I've learned to detach from my stepmom's behavior (most of the time).
Hugs and prayers,
Amy