Ring of Lies — Rachel Lynne

Jewel of the Night Series
A café owner and an ex-cop must unravel the mystery surrounding a hot blue diamond in order to stop a cold blooded killer.
After a childhood lived on the road with a free-spirited aunt, all café owner Ivy Michaels wants is a normal and uneventful life, but when her aunt is found floating in the Savannah River, Ivy inherits an heirloom blue diamond and a killer bent on keeping the past buried.
Dom Riordan is an ex-cop obsessed with finding his mother's killer. A chance meeting, and a glimpse of evidence he's been seeking, convinces him that Ivy Michaels is the key to solving the crime. Dom devises a plan to date Ivy and ferret out the truth but he didn't count on losing his heart. As a ruthless killer closes in on Ivy, Dom will risk everything to keep her safe.