how to get mother to stop smoking in the house?

Me and my mother have a roommate situation right now as neither of us make enough money to live in a good neighborhood alone. I really don't want to have to live in the ghetto and don't want that for her either but I'm having a problem living with her smoking. I have terrible allergies and respiratory problems which may or may not be related to her smoking when she was pregnant with me and around me as a child. I can't stand being in the general vicinity of cigarettes. I've tried to get her to smoke outside and she just says she's already cutting back on smoking.

Does anyone have any ideas on what I can do or say to get her to stop smoking around me? I have an air filter but it doesn't help much.