Answer:
A band in the movie are Satan worshipers because they want to become very famous. They read in a satanic book that they need to sacrifice a virgin. They meet Jennifer, she is far from a virgin but her friend over hears the band saying they defiantly don't think Jennifer is a virgin this angers the friend and she tells them that she is a virgin and she is better than them. The bar that they are in burns down and as people rush out Jennifer is separated from her friend and the band take Jennifer were they Sacrifice a "non pure spirit" and she turns into a demon.