Poshes were a hybrid that came from the Boutique. With the Pinks being immune to the Juggs virus, it was tried to use the Pink chemicals on a Juggs. The chemical lead to the return of the mind of the girl with just the lust of pink like the rest of the Pinks, but her body stayed that of a Juggs, milk and all.
The Poshes had to fight internally the urge to spread the virus. Their minds knew it was wrong and it would lead a girl into the mindless path of the Sisterhood, but the body urged them on and on. The Poshes though took on another trait. They had the extra need to always look perfect, flawless hair, makeup, nails and outfits. They had the need to be to the nines all the time.