The Shining City by Kate Forsyth

Rhiannon, a wild and fierce half-human girl, tamed a winged horse to escape the vicious satyricorn tribe who raised her. In the human world, the handsome apprentice-witch Lewen has convinced her to stay with him and learn to use her strong magical talents. But before her training can commence, Rhiannon must answer for a past crime in... THE SHINING CITY

Imprisoned in Sorrowgate Tower, Rhiannon awaits trial for murder and treason. While her days are spent in anticipation of Lewen's visits, her nights are haunted by the malevolent ghost of a dead queen, hungry to live again. But not many care to listen to the prophetic dreams of a girl who has already been convicted in most people's minds.

Then Lewen begins to cool toward her, and Rhiannon suspects one of the princesses has worked a spell to steal his heart. In a world filled with dark spirits and forbidden magic, conspiracy and intrigue, Rhiannon vows to win back her lover and escape once more, to save the land before it's too late....

This book is part of the "Rhiannon's Ride" series.
Here are some other books from this series: