The Night Garden (Fairytales of the Loch #1) by Nicole Northwood:
 
Ellie Blue Callaghan isn’t ready to give up her wild ways. When she turns nineteen, she’ll be sent to Blossom Preparatory Academy to train to be a proper sorceress, adult, and wife for Colonel Gallagher. Unfortunately, Ellie loves the wind-swept countryside of Loch Gàrraidh, her untamed and turbulent magic, and the hallucinogenic experience of a fantastical drug called Allure, and she can’t imagine a life without them.

Max O’Carroll failed out of Blossom Preparatory Academy and was cursed for eternity. His affliction will be broken if he finds true love, but nobody in recent history has even fallen for a Bèist—a being that presents as a feral cat by day and takes their original human form by night. But when Ellie and Max meet during a twilight garden party and connect over wine and a moonlit swim, they soon realize their perception of love, freedom, and control are very different from what they’ve been taught to believe.

Getting tangled in Max’s terrible enchantment could mean disaster for Ellie’s future, but only if Blossom Preparatory Academy can find her…

Content warnings can be found on Nicole Northwood's website.