The Freedom Broker (Thea Paris 01) by K.J. Howe

Kidnap negotiator Thea Paris has spent her entire life with survivor's guilt, following an unspeakable childhood tragedy. At eight years old, she watched, frozen in fear, as her twelve-year-old brother, Nikos, was abducted from their home in Kanzi, Africa. Although he was recovered nine months later, he was never the same after that; worse, Thea discovers that she was supposed to have been the target.
This defining experience drives Thea to become one of the top operatives in the field of kidnap-and-ransom consultancy. Nicknamed "Liberata" because she once secured the release of a captive from the Sicilian mob without her client paying a cent, she travels the globe trying to bring hostages home—mostly through negotiation, but occasionally through more forceful means. She is very good at her job.
Twenty years after her brother's abduction, Thea's worst nightmare is revisited when her father, oil magnate Christos Paris, is taken on his sixtieth birthday. He disappears...