Ed, YOU ARE right by her side... much to your detriment... You need to figure out a way to not be so emotionally invested in her every malady (As hard as I know that is!) and start healing yourself... THAT will help you more than anything.
I cringe at the thought of being called a "Vet" As I've only been on these boards for a few months... but I've learned from some amazing people and feel that I'm making SOME progress... But I'm FAR from where I want to be... But either way, I appreciate you appreciating me!
Either way... You're 100% right about her addiction... You CAN'T fight that fight for her... She knows you're there when she needs you... and as tough as it might be to hear... that's a form of enabling... Keep the focus on you and S... Let her feel the pain of loneliness that you feel by simply being a better person and a better father.
Her heels are dug in... so it's time to dig YOUR heels in too... I know you can do it.