Starshell by Adara Vesper

As a newly freed prisoner, Lisia is ill-equipped to participate in the grueling training program that prepares the elite to venture offshore, though she must, as part of her probationary penance. It also happens to be the safest place to hide from another prisoner who is out for her blood. Unfortunately, her plan to protect herself goes awry when she draws the attention of a disreputable acquaintance, stirring up more trouble than she already had on her to-do list.
Her situation doesn’t improve when a chance encounter with a striking stranger triggers magic that illegally marks them both, a secret that could cost them their lives if discovered. The undeniable attraction she feels towards him, and finding out he will be her training instructor, exacerbates her surplus of problems. Graduating the training isn’t the goal–it’s the starting line in a fight for her life.