The Lilies by Quinn Diacon-Furtado

One of Us Is Lying meets A Good Girl's Guide to Murder in this don't-dare-to-look-away dark academia thriller that explores how secrets can rot an institution-and the people who uphold it-from the inside out.
Everyone wants to be a Lily.
At Archwell Academy, it's the ticket to a successful future. But like every secret society, there is something much darker beneath the surface ... sometimes girls disappear.
When four Archwell students find themselves trapped in a time loop, they must relive their worst memories, untangling the Lilies' moldering roots and unraveling the secrets at the core of their school ... before they destroy their futures forever.