Sage Dursley and the Unusual Letter

Sage thought her life couldn't get worse, first her mum dies, then her dad sales their houes and moves them in with his parents, then Sage gets a letter saying she can go to Hogwarts, but someone is after her new friend Lily, someone from Lily's dad past thought to of been dead the last 21 years. They want revenge on Lily's family by taking it out on Lily. And it's not Voldemort.