My mom smokes, too, and she is also a registered nurse.

I'm sorry, but I think the only thing you can say is that you care for her and her health, and it would mean a lot to you for her to quit smoking. It's bad for your health, too. I think it is your mom's choice, and you (and I with my mom) have no control over that choice. The only way for her to quit is when she is ready, and you will be there to support her when she is. Quitting is a hard thing to do when people have been smoking for years, I think the only way for her to quit is when she's determined and ready.