My Sister Has To Have An Operation. She Has A Habit Of Smoking

good morning, my sister was told yesterday that she has to have an operation on her back to fuse somethings together and that she had to quit smoking first. she intends to start the chantix in the next few days. what i'm wondering, she is afraid to talk to her doctor to ask him so i came to you. she also smokes marijua, i don't know how to spell the stuff, but anyway i want to know if the pot smoking will show up on the tco2 test the doc told her she had to pass in order for the operation to work sucessfully, what should i tell her.