Enthusinazi
Someone who is a totalitarian fanatic. Hates anyone who likes their idol's rival or competition. Thinks being a fan to that celebrity or product makes them superior and anyone who doesn't share their enthusiasm for it/him/her is subhuman.imposes their favorite object upon others.
She is a hardcore Beyonce Enthusinazi,she will kill and die for her, as a Rihanna fan I'd advise you to steer clear off her way.