Seeing as how she’s a heavy smoker, she probably doesn’t care about her own health. You need to convince her from a different angle; you telling her that she needs to see a doctor because she’s in bad health isn’t going to do anything.

Get her a lil cig flavored vape and see if she likes it

My dad is also a HEAVY smoker, you’ll never see him without a coffee in one hand and a ciggy in the other. Unfortunately my dad also has many other health conditions including 20% lung capacity and he no longer cares. I’m 20 and my father isn’t going to live to see me having any kids or go graduate college or anything like that. Tell her she’s shortening her life, you will both miss so much of each others lives unless she at least slows down. Don’t tell her to quit, that’s just going to stress her out and make her want to light up. Just tell her to be mindful of how much she is smoking, bring up that it’s an expensive habit and that it stinks or something like that. Telling her to quit will do nothing, give her *reasons* as to why she should. I hope she listens ❤️

Unfortunately you're Fighting an uphill battle. She knows that smoking is hurting her but her physician going to tell her to stop smoking, she doesn't want to hear that so she'll put off going as long as she can. All you can do is love her through it. If you're frustrated, which is reasonable, tell her that it's because you're worried and you love her. Unfortunately I think you may have to give into the fact that she doesn't want to hear that she has to quit therefore she's not going to go.

Vaping is just changing one bad habit for another