My heart actually breaks reading this. We are just so unaware of the pain we cause to loved ones while we are in the midst of it all. However, you are not selfish to want to live your life!
I’m sorry the GP wasn’t more helpful. Yes it’s the diazepam is what’s making her zombie like especially if she’s combining it with her codeine pills. They both have a sedation property which will conk her out.
I think you have to be honest and put it to her that if she wants to tell the truth and get help you’ll support her all the way but you can’t stay and watch her destroy her life and ultimately yours too. You deserve to be happy so please don’t feel guilty for this. The fear of you leaving might just give her the motivation she needs. Just remember she has to want to do it herself or she won’t be able to get through it.
You really have tried everything but the ultimatum. Addiction is so hard and it really impacts on everyone around the person. I really hope you can get through to her. And please, anytime you need to vent or have a question, message me. You need support too.