Who is Darleen, Letitia, and Neilette from The Last Continent: A Discworld Novel and what is their importance?

Darleen, Letitia, and Neilette are a troupe of female impersonators—with Neilette being an actual female, filling in for her brother, who has quit the act—the so-called "ladies" find protagonist Rincewind's Luggage along the roadside and rename it Trunkie. It gets them out of several close scrapes. In the town of Bugarup, as he flees the Watch (police), Rincewind hides in the ladies' wagon. Darleen and Letitia manfully fight off assailants, while The Luggage disables watchmen in an alley.