Depths of Blue by Lise MacTague

For Torrin Ivanov, life is a bargaining table. Every planet is a new business opportunity. Legality is optional and supplying one side in a local civil war always adds up to profit. Jak Stowell is at war within a war. A woman hidden in the heart of a male-only army, her brother's murder has left her desperate for vengeance. Her skill as a sniper gives her both the disguise she needs and paves the way ever closer to her real goal. She kills efficiently, without remorse. Putting down an off-world smuggler will be no different. A moment's hesitation. A flicker of doubt. Two women on a collision course set off a chain reaction of intergalactic intrigue--and awaken a dangerous passion that could cost them their lives.