I think you need to deal with your real issue op, this person who is putting in you. They may well be being very selfish and leaving you feeling like you can't say no while they do nothing tonhelp themself, but that is their issue and your issue with them. Otherwise generalisations can be made all around making almost everyone selfish.
My friends dmum who is addicted to food and my friends has to run around after her and help her all the time. Shes had a band fitted but that hasnt changed the underlying reason for her addiction so she still keeps eating more.
My cousin whose addicted to pot and coke qnd has.much help from the NHS but still goes back to.it because the reason for his addiction hasn't been dealt with.
My dsis friend who was told not to give up smoking when pregnant because she'd given up coke and x as soon as she found out. Her hv told her it was very unwise.
My friends dad has emphasimia, he continues to.smoke. He's depressed and stressed and it stops him having a breakdown.
Yes, we all got very frustrated when (except for last one) they went back to their addictions, but theres always a reason for it. You need to stop ranting in general and look specifically to your friend qnd decide if they are being selfish, why they are, what you can do to stop yourself being put upon and how you go about it.
My friend made her.mum pay for a dog walker. Her.mum is addicted but expecting her daughter to drive 20 miles there and back twice a day to walk her dog was unfair and very selfish that her mum tried to guilt her. My friend put her foot down, either mum paid for a walker or the dog was rehomed where it could get plenty of walks.