A Deceit of Lapwings — Dee Morrison Meaney

This is the second book of the Branwen trilogy. The Vikings have claimed control of the land and Branwen is free at last to marry her Viking lord. But, if she becomes Thorkell's wife, she must reject her heritage, give up her powers. Then, as an ordinary woman, she is without protection against those who hate her--including the king Thorkell serves.