Upon realising he has a super-fan, the emotionally volatile singer of a struggling band initially feels flattered; but he allows this feeling to darken into something obsessive and unhealthy as he and the fan begin an illicit dance of mutual shadowing, pursuing each other without ever actually meeting. So when the fan’s interest begins to wane, her happiness and the wellbeing of those around her is threatened by his unwillingness to give up her adoration.
I think Richiev is on the right tack, but this being the age of the internet:
When her fansite for her favorite band goes viral, an obsessive teen finds herself being stalked by the emotionally unstable lead singer.
This is predicated on the assumption that the story entails a pas de deux of two quasi-OCD people She starts out as obsessed with the band as he becomes with her.