Lady, Thy Name Is Trouble by Lori L. MacLaughlin

SPFBO6

Trouble is Tara Triannon's middle name. As swords for hire, Tara and her sister Laraina thrive on the danger. But a surprise invasion throws them into chaos... and trouble on a whole new level. Pursued by the Butcher, a terrifying assassin more wolf than man, Tara and Laraina must get a prince marked for death and a young, inept sorceress to safety. There's only one problem - eluding the Butcher has never been done. Aided by a secretive soldier of fortune, they flee the relentless hunter. Gifted with magic and cursed by nightmares that are all too real, Tara must stop an army led by a madman and fend off an evil Being caught in a centuries-old trap who seeks to control her magic and escape through her dreams - all while keeping one step ahead of the Butcher.