So I came across this naturally throughout the game without even going for it (or knowing about it to be honest). In the story I am up to my first mission with the freedom pals and got the side quest to help Mrs Cartman (having already previously finished her prior side mission of distributing her items at Skeeter's Wine Bar)
*** Spoiler - click to reveal ***and simply during the battle your only available move 'charms' the prostitutes to your side so I spent my two turns attacking on using the charm slap on them whilst also using my time-fart to cancel the Pimp's turn and in two attacks from my charmed prostitute,
I had won the battle and earned the achievement.
Hope this helps