How to help my mom to quit smoking?

I am very serious here. She has been saying for a long time that she is gonna quit. Shes a long time smoker and shes been saying that she'll call her doctor for a while now. I try to talk to her but she ends up getting mad at me for who-knows-what reason. I love her and I don't want her to die because of a stupid choice she made 25 years ago. It saddens me and i was talking to her earlier and i said she lied because she promised she'd quit if something happened (personal) but then she said I lied before to and its bad. But, I said that lies can't kill and she said yes they can. So i said mine can't but yours can because you have not quit yet. she did not answer so i proved her wrong. I love her and i need advice. Good, serious advice.