One of my best friends are obsessed with cheese.?

my best friend is obsessed with cheese she wont go to the mall or the movies with any one no more unless we promise well buy her something with cheese and if we ask her why cant you buy it shell say im saying up for cheese DEAD SERIOUS shes always have been a serious person got straight as and never got into drama and now its scarring me and i know shes not ditching cause if we say well buy her cheese shell come and just sit there playing with cheese like at the food court at the mall or with the nachos during a movie its scaring the crappers out of me please help!!!!!!!!!!!!!!!!!