She Wont Have A Relationship With A Pot Smoker

I have been seeing K for 3 months. I am by no means a big pot smoker. I have used marijuana for the last 14 years on and off. Mostly I do it once a week when I am with friends but for the last few months I have only smoked on one occasion. This made K very upset. What I don't understand about K's position is its extreme nature. ie "I will not be in a relationship with someone who smokes pot period". That means even if I smoked once a year and not in her presence it would not be good enough. As long as I am in a relationship with her I must never smoke ever again. Every time I try to get her to explain to me why she has such an extreme take, she cant give me a single honest explanation. The arguments are all circular. She has a pre-conceived notion that pot is somehow not conducive to a healthy relationship no matter how infrequent its use is. I may be willing to not ever have it again but I need a real explanation from her as to why, and she is not able to give me one