Mortal Faults by Michael Prescott
Approx. 101,620 words.
Published on November 19, 2011.
Private security consultant Abby Sinclair identifies stalkers and neutralizes them - by any means necessary. When Abby is hired to protect a U.S. congressman from a mystery woman shadowing him at public events, she has no idea that she'll soon be intruding on a secret federal investigation - or that FBI special agent Tess McCallum is about to come back into her life.