Seventeen-year old Jen Hargrove arrives at Mount Holly Amusement Park believing her summer job will help heal both her mind and heart. Because while no one could ever accuse her of having a blissful, normal upbringing, her unhappy childhood was nothing compared to the living hell that masqueraded itself as her junior year at Chesterton High.
(your hook starts here)
Ten months have passed since her boyfriend, Michael Garrison, was murdered during an armed robbery. Unable to get past her role in the sequence of events that led to his death, Jen continues to be haunted by guilt and regret. (stop) And so, more than anything, she longs for the chance to see Michael one last time.
(start) Jen’s hopeful enthusiasm quickly fades when, just days after her arrival at the park, Jen experiences ethereal visions of a young bride. At first, she fears her tenuous grip on sanity is slipping again. Soon she’s wishing it were only that easy.
No mere hallucination, Lydia McKinley, the long-deceased daughter of the original park owner, invades Jen’s waking and sleeping hours, compelling her to solve a decades-old crime. Knowing she’ll be headed back to Chesterton Memorial Hospital’s mental health ward if she can’t stop the onslaught of the visions, Jen sets out to discover the truth. Her dilemma: how to solve the mystery without scaring off a new love interest and losing what’s left of her mind?(stop)
Focus on main elements. Why is Lydia picking Jen? Does the bf factor into the story beyond the fact he's dead and she's in mourning?
This is a pretty standard plot. I'd be looking for something that elevated it beyond what is run of the mill.