In the Line of Ire by Camilla Chafer

When Private Investigator Lexi Graves receives an expensive bag from her new husband, she’s delighted… for all of five seconds. That’s exactly how long it takes her to realize it’s a fake. Then another fake bag turns up, along with an outraged mall manager that is desperate to find the culprit before the mall’s impeccable reputation for selling quality goods is tarnished. When the initial investigation takes a murderous turn, Lexi knows she has no time to lose.
Going undercover would be easy if Lexi could convince anyone to talk. Then the FBI and Solomon Detective Agency collaborate to track down the culprits, and Lexi is further tasked with exposing the master mind behind the recent flood of fake goods. The counterfeiters, however, are smart enough to cover their tracks and the suspects are all seemingly innocent. Yet, one of them is a murderer… and ready to strike again.