The Floating Outfit 12 by J.T. Edson

With a Colt in her purse and a price on her head, Calamity Jane was fair game for every bounty hunter in the Territory—until she hooked up with the Floating Outfit's "best-dressed man," Mark Counter, the segundo of the Rio Hondo Gun Wizard himself. Counter was a man to be reckoned with. A man whose second name was trouble!