((((threeforty))))
I hope you do seriously think about taking the advice offered about finding some naranon or alanon meetings for yourself, and your Mom. Meetings are all different because of the mix of people, so hopefully you live someplace where you can try a few meetings to find a place where you feel the most comfortable. Also remember, it takes time. It's amazing, but in time you will start to have your own understanding, have patience.
What you're feeling is so understandable. I cannot begin to imagine having a parent tell me this. Like you said, now the last 10 years make sense, but it sounds like it doesn't make sense either in a way. Addiction is addiction, but it seems like different drugs sometimes throw in a few of their own things.
Stay here! Read! Finding some meetings! Welcome!