My reply about oxygen had to do with the word "critical," so I guess definitions can vary. Usually oxygen is authorized when it falls below 89.
Sounds like she has copd at the least, any oxygen sat less than 87% is dangerous. a person can't qualify to get oxygen at home withoutmeeting certain criteria. If her sats remain in the low 80's her brain isn't receiving enough oxygen to even make the decision not to use it. if she continues to smoke she will die. If she continues to refuse oxygen she will die. Our bodies require oxygen to function. Its vital for sats to remain above 87% at least most of the time. if she has severe copd as I suspect, her o2 sat needs top be between 88-92% optimally. Too much oxygen can also be harmful if she is severe copd.
I asked this same question a while ago and was told when it dropped below 80. There may be different opinions on this. When you say her blood oxygen is 82 or 83, is that at rest or when ambulatory? Is she capable of dressing herself, bathing herself, etc.?
As for smoking, that is a bad idea. Smoking while using oxygen is even worse. A nurse told me recently of someone blowing herself up doing that.