How to handle MIL smoking weed while visiting?

My MIL arrived yesterday for Christmas. She suffers from chronic pain and used weed to help alleviate her pain. She has a prescription and also grows her own (were Canadian so this is legal). I have two going kids and an infant- I don’t want them around weed, especially the smoke. My infant is a premature baby and has under-developed lungs. She’s not supposed to be anywhere near smoke and I have to be very careful of even things like perfume around her right now. I also find that smoke really clings to fabric and I don’t want my home reeking of weed and then having to professionally clean or replace my curtains, couches, etc.

I have already asked if she would use edibles while visiting to remove the smoke aspect. But she doesn’t like edibles and refused. I said ok, but said I could not have her smoking in the house under any circumstance. She is also complaining about smoking outside as it’s too cold (I mean it is -30C out so I understand). I’m fairly certain she’s already smoked in the house at least once. Our guest bedroom is in the basement (we live on a hill so the basement opens out into our backyard) and I went down there to get things from the freezer and the smell of weed was very prominent. I wasn’t planning on going into the guest room, but I did knock and when she answered the room had a very strong smell of weed. I asked if she’d been smoking in the room and she claimed the smell was due to her just having come back in from a smoke. I think that’s a load of crap honestly, but I didn’t press the issue as my infant started crying upstairs.

I do want to revisit the issue. She’s staying until the 28th and she smokes 3-4 times a day. My guest room and potentially the rest of our basement (we have a bar and living room-style set up down there) is going to reek and I don’t want to deal with that. It’ll be very costly. Already the smell is bothering me. I’m angry that she smoked in the house after I told her not too. I’m hoping the smoke and smell doesn’t start affecting my kids (I’ll be keeping them out of the basement, but that is where our big TV is and we usually watch family Christmas movies on it).

I’m concerned for my daughter though. She’s spent the first 6 months of her life (she’s 9 months now) in the NICU and I don’t want to go back to the hospital. I just can’t believe a grandmother would put their grandchild at risk like this. I get it’s cold out, but bundle up. She knew about this before she came to visit (I warned her even before the plane tickets were booked as well).

I’m thinking I’ll just let my husband handle it when he gets home. But, I don’t know how to prevent this from happening again. I have half a mind to ask her to leave honestly.

Also if you know how to get the smell and smoke out of the house please comment. I’m not a smoker and either is my husband so this isn’t something were used to. I don’t really want to open windows because it’s so cold and it’ll cause our heater to work harder which will hike our utility bill. But I can’t think of another way.