Hi there. Firstly your son needs to be your priority, if he’s missing days off school and she’s lying in bed, that’s awful! I know you work but seriously I wouldn’t be leaving my child in her care, maybe you should approach family members and raise your concerns. Be warned though, they will probably tend to take her side as she will probably down play it or even worse turn it around on you. My husband did exactly that! They even thought all his drug problems were due to him not wanting to be with me anymore. That was until he went to live with them and he caused chaos there!
Secondly there is nothing you can say or do to make her change, as hard as it is try not to take it personally. Her mind has now been rewired to all things addiction, all the reasoning and trying to get her to see sense will be wasted. You need to focus on you. Maybe seek help for yourself. Al anon was a life saver for me. It seemed odd at first but the more I went the more I got it.
You need to try and build a good life for you and your son. Whilst she is an addict you won’t be able to do that. There will be a lot of tears and tantrums along the way but there is light at the end of the tunnel but you have to follow through with what you threatened otherwise this will be all of your lives forever.