I thought with my sister 400km away I was save from this

I know I can't go around and forbid people to smoke pot in their own rooms, but do they have to open the windows too?
There are people who simply hate the smell and get nothing out of it but a headache.

It's still 29°C in here, I really don't want to close the windows.
*contemplates the essential oils*
*hopes a drop of eucalyptus under the nose will do the trick*