The Asset by Connie Myres

She followed the rules. They signed her death warrant.
Reyna Cruz doesn't just watch the crowd; she reads the silence. As a Diplomatic Security Service agent, her survival depends on noticing the things everyone else misses.
On a rainy morning in London, Reyna spots a glint in a window that shouldn't be there. When she calls it in, Command orders her to stand down.
She has two choices: Follow orders and let a Senator die, or break protocol and become a rogue element.
Reyna chooses the target.
Now, she is "The Asset"—a liability marked for liquidation by her own government. Hunted through the streets of London with no backup and no exit strategy, Reyna has to rely on the only skill that matters: the ability to disappear.
But she isn't the only predator in the city. A mercenary named Jack Wolfe is watching. He's looking for a ghost, and he has an offer that will change her life:
Die as an agent, or live as a shadow.
The Asset is a high-octane prequel short story set in the world of the Onyx Tactical series. It tells the origin story of Rey, the team's most elusive operator.