Friends smoking pot?

My bestfriend smoked twice a few years ago but this past week she has hung out with people and smoked every night. I refused to hang out with her tonight because I am disapointed and upset. Can I tell her that I don't want to hang out with her if she keeps smoking? She forgot to pick me up because she was too high. I feel like her getting high is now more important than us hanging out? Can I give her an ultimatum to stop smoking or stop being my friend?