Sacrifice the Knight by Emilia Finn

Sacrifices are never ideal, but to win the game, sometimes the knight must fall.
Katrina Blair is a single mom to a daredevil teen, which means she has no time for fruitless endeavours such as dating.
Why? Because men are all the same: liars, thieves, and unreliable a**holes.
Pregnant at fifteen and deserted by the father long before their son was born, Katrina learned her lessons early in life and has built an impenetrable wall that keeps the weak away.
But Eric DeWhit isn’t weak, and he’s been lingering on Katrina’s side of the diner an awful lot lately.
Eric’s former life as an undercover agent is not open for discussion, so he chooses lame jokes instead, and lets them flow as regularly as Katrina’s coffee pot. Her sneaking glances under lowered lashes assures him that she’s attracted too, but every time he asks for anything more than a burger and fries, he’s shot down with a stern “No.”
Katrina is set in her ways and insists on maintaining the strict rules that have gotten her through fifteen hard years, but she’s about to find out there’s an exception to every rule, and Eric might be hers.