my boss is a chronic cigarette smoker..

How do I politely tell her the smell is unpleasant?
When I first started I didnt have the super sniffer because I was early in my pregnancy. But now the smell is horrible! It makes me want to hold my breath. We work in a very small space with limited mobility and I can't take it anymore. One manager already mentioned it to her but she blew it off... what should I say or do?