Destiny by Gillian Shields

In Destiny, the fourth and final book in Gillian Shields’s romantic, gothic Immortal series, Helen, Evie, and Sarah, the Sisters of the Mystic Way, must use their powers to battle for their souls.
 
Malevolent forces haunt Wyldcliffe Abbey School for Young Ladies, the girls’ elite boarding school on the English moors. Dr. Franzen, an evil man from Helen’s past, has taken over as headmaster. And while Helen longs to believe her mother, the priestess of a coven of dark witches, has reformed, she fears her mother cannot be trusted.

At least Helen can cling to the prediction that a love "beyond the confines of this world" is waiting for her. Could this be Lynton, the mysterious music student who visits Wyldcliffe for his lessons?