Book Rootbound — Margaret Owen

Corona's neighbouring kingdom, Astera, is a famously reclusive island, so when a suspicious invitation arrives welcoming Rapunzel to the Asteran princess's coming of age ceremony, she accepts. Little does she know she's about to plunge herself and Eugene into a tangled knot of political intrigue and magical secrets.
Thrust into a power struggle between Astera's princess, its king and a mysterious secret society, Rapunzel and Eugene fight to defend their home from an unsettlingly familiar magical threat and discover that their past can either hold them back or help them blossom.