The Water Witch (book 2 of Fairwick Triliogy)

After casting out a dark spirit, Callie McFay, a professor of gothic literature, has at last restored a semblance of calm to her rambling Victorian house. But in the nearby thicket of the honeysuckle forest, and in the currents of the rushing Undine stream, more trouble is stirring. . . .
 
The enchanted town of Fairwick’s dazzling mix of mythical creatures has come under siege from the Grove: a sinister group of witches determined to banish the fey back to their ancestral land. With factions turning on one another, all are cruelly forced to take sides. Callie’s grandmother, a prominent Grove member, demands her granddaughter’s compliance, but half-witch/half-fey Callie can hardly betray her friends and colleagues at the college. To stave off disaster, Callie enlists Duncan Laird, an alluring seductive academic who cultivates her vast magical potential, but to what end? Deeply conflicted, Callie struggles to save her beloved Fairwick, dangerously pushing her extraordinary powers to the limit—risking all, even the needs of her own passionate heart.