I [26M] can’t get my partner [24F] to stop smoking

My partner of 5 years and I had our first child back in January last year, when we found out she was pregnant she stopped smoking on the day. Throughout the whole pregnancy she remained smoke free. Post partum, maybe 2 or 3 months after it, she began wanting to go to parties and there, of course, she’d just have a smoke because “everyone else was doing it”. I didn’t think much of it, besides letting her know to not systemize it. But she did. Every 2 weeks or so she’d go out to party just so she could smoke. She began smoking again shortly after. I told her how I disapproved of it but she waved it off. Then she stopped, or so she told me. A few months later, she told me that she hadn’t actually stopped, she had been smoking at work, when I wasn’t at home etc. She once again promised that she’d stop, but I kept finding cigarette packs hidden around the house, buds outside etc. She keeps moving the goalposts about it. At first she claimed she’d never smoke at home, when she did, the said she’d never smoke when the kid is awake, when she did that, she said she’d never smoke when he was nearby. I can’t argue with her, every time I try to talk about it she gets so angry. How can you teach someone that smoking is bad and to stay away from it when moms over there smoking? I don’t know what to do. It smells disgusting, the whole room stinks when she enters. I need advice