groupie

noun Informal.

1. a young person, especially a teenage girl, who is an ardent admirer of rock musicians and may follow them on tour.
2. an ardent fan of a celebrity or of a particular activity: a tennis groupie.

noun slang

1. an ardent fan of a celebrity, esp a pop star: originally, often a girl who followed the members of a pop group on tour in order to have sexual relations with them
2. an enthusiastic follower of some activitya political groupie