Parents who smoke

Both of my parents smoked for a long time but my mom had to quit when she went into the hospital and lost half a lung. My dad continued until I berated him to try vape pens and now he's cut back on his nicotine intake wonderfully. Mom has started back up again, and I made her promise not to smoke in my car. Well she broke it. So now, I need to get advice on how you got your parents/sibling/SO to stop smoking. Please help, she is sick all the time and is so underweight. She needs to quit or something bad is going to happen again