Drug Abuse -- Please help

Hello - 

I just discovered that the my ADHD diagnosed wife of about 9 months has not only been abusing her Adderral XR capsules and tabs but also purchasing street level meth pills to self medicate. She has kept this from me for months and I only discovered this when going through our finances this weekend. When I asked about it she told the truth but I am at a loss for words. I have never hid anything from her in the over three years I have known her. I try to keep a household schedule, help her organize but not push or baby her. I feel like my trust has been shaken to the core and I do not know the next step. She doesn't have many friends and I don't know what will happen to her if I leave her. I fear I will never be able to trust her again. My apologies if there are any typos I am still very shaken up. At this point I am just asking for advice.