The fact that she had a lengthy addiction in the past doesn't have to mean that she was smart about her addiction, or even that she took responsibility for supplying her own habit, or even learning her own doses.
When I first started taking pills, I got them from the guy I was dating, and my dad. I trusted them a lot, and would never ask what or how much they gave me. After I had a couple of different effects from pills, I'd just tell the guy I was dating what I wanted to feel and he would give me what I needed, and he told me to just tell my dad that my back hurt really bad, and he'd give me my favorite. It wasn't until much after I left him, and got back into the pills, that I ever took the time to figure out what drugs I was taking, or did the research to figure out how much I should be taking.
I was very young, and super stupid at the time. All I cared about was getting high. I didn't give a damn about the mechanics of the drug, the process of ingesting them, or the culture(s) that revolves around them until over two years later. It's a sad way to be, but it happens. I'm just glad that I view mind/body-altering substances in a much different light now, and I'm glad that OP seems to be attempting to do so as well.