My sister smokes(like a chimney!)andi love her dearly. what do i do/say to convince her to stop smoking?

Not Much: Every smoker that's not in a cave knows it isn't good for them & if they say they want to stop but don't, they aren't ready to stop. They will stop when they decide they want to. Trying to talk to them or convince them to stop is more likely to cause problems between you since she will feel she needs to pick one of you and you won't win. You can make it clear she cannot smoke in your car or home.

Second hand smoke: Although it isn't your responsibility to get your sister to stop smoking, it is important to convey your concerns to her. Let her know how much you love her. It is also important to set limits because her habit could kill you. No smoking in your car, your home, your presence. She needs to understand the damage that the second hand smoke she generates can do.