How to deal with pushy mother in law and my daughter?

My grandmother is just like that. I go over there, and I immediately want to leave, but she smokes heavily, and I know once I leave she'll be smoking around my baby. So I stay, but I do tell her if I've had enough, and we'll leave if I just can't take it anymore. I just can't stand it. I don't know how else to handle this, other than to tell her how you feel. It'll be hard, but give it a try.