In the Black - Tales from the Edge, #1

When Sam Keller left the military, she ran to the far end of the galaxy. Now she captains the Bonnie Belle, a spaceship full of courtesans who bring a little pleasure to hard-up men and women on distant mining colonies. When one of the women turns up dead, it's Sam's job to find out who killed her, and fast-time is money, as far as the Guild is concerned. Marshal Daniel LeClair is as tough as steel, and quick on the draw.
But when his vacation gets replaced by an assignment to help find the killer, he can't help angling for a little action with the hard-charging captain. She's got brains, attitude, and a body he wouldn't mind investigating. Sam, six months lonely, might just indulge him. But the Guild wants the case closed yesterday-no matter what the truth might be. With pressure coming from all quadrants, Sam and Daniel clash over false leads, and who's going to be on top.
But when the killer threatens the Belle again, romance will have to wait. It's a captain's job to save her crew, no matter what the cost-and Sam's not going to let anything happen to those under her command. Not again. Even if it threatens her chance at happiness with Daniel.