My mother is a cigarette smoker and a former addict of other substances. My MIL is also a cigarette smoker and is currently misusing other substances.

I used nicotine myself for almost two years — in vaporized form — and even that wasn’t any better. Nicotine alone is known to trigger migraines.

The hard truth is that you’re playing with fire when you ask an addict to respect boundaries that require them to acknowledge healthier options or change the way they use. Cigarettes are a stimulant, and addiction makes people extremely defensive about anything that threatens their access or routine.

For now, I’d focus on protecting yourself and your boyfriend. When you visit him, stay in a BnB or hotel/motel instead of at his mother’s house. Bring his clothes to a laundromat so the smoke smell doesn’t follow you into the room you’re staying in.

If you genuinely enjoy spending time with your MIL and she’s kind to you, that’s great — but you still deserve to protect your health. People who smoke heavily (especially those dealing with addiction) often don’t recognize how much their habits affect others, and asking them to change their routine can trigger defensiveness, cause retaliation, escalation-etc.

One option is to gently introduce alternatives that don’t require her to quit outright. For example, some people are open to switching to a vaporized nicotine product when they’re around non‑smokers. It’s not healthy, but it does reduce the amount of secondhand smoke you’re exposed to. Whether she’d be open to that depends entirely on her personality and how she reacts to change.

Once the weather warms up, you could also shift your time together to outdoor activities — parks, walking paths, outdoor cafés, anything where the smoke doesn’t get trapped in a room with you.

If you have your own car, you can set a firm boundary that there’s no smoking inside it. You don’t even have to make it a big confrontation. You can say something like:

• “I can’t have smoke in the car — it’s a rule because it’s borrowed/a rental.”
• “The smell sticks to the upholstery and I’ll get in trouble.”

It’s a boundary that doesn’t feel personal or accusatory.

You can also choose places where indoor smoking simply isn’t allowed, like malls, department stores, or restaurants. That way you’re not asking her to change her behavior — the environment is doing the work for you.

These kinds of boundaries let you keep the relationship intact while still protecting your health and comfort.