The first in the series The Elemental Masters.
Small sample of the beginning of Chapter 1:
Rosalind Hawkins answered the door with her entire being in a knot of anxiety; expecting yet another aggressive creditor, she schooled her face into a calm she did not feel. Outside, the dreary, drizzling day was giving way to another dreary night. The home that had once been her sanctuary was now under siege --- and no longer hers.
Summary from www.mercedeslackey.com: