I would kindly ask my MIL not to smoke in front of me as I'm 2 weeks into a quit. If she is supportive I'd relax and enjoy dinner and her company. If she refuses not to smoke I would take my spouse aside and say that this environment wasn't healthy for my quit and that I was going to have dinner at the non-smoking restaurant down the street. If my either of them had an issue with that I'd look at it as their problem, not mine. I am only responsible for my own reactions, not my spouses or MIL.
You’re two weeks quit and very agitated. You’ve just finished work and you are looking forward to going home to relax with your spouse. You get through horrible traffic and do your best to ignore your neighbour’s dog barking at you as you enter your house...
Surprise! Your mother-in-law is over for dinner. The worst part, she is a chain smoker.