mom smokes

About two years ago, I walked in on my parents smoking in the backyard. I was very pissed off since they had always told us that they'd never smoke before. My dad rarely does now, but my mom on the other hand feels totally comfortable with smoking around us. I AM NOT OKAY WITH THIS. I've tried to talk to her about it but she never listens to my opinion. Idk what to do. I fear for her health in the future. And I also don't want her to be smoking around my kids when the time comes. 
I just don't know how to handle this. My only plan atm is to talk to my family doctor about it and see what she says. 
Any advice???