Babes Behind Bars by Allan Mora; Lester Lake

'The hard-bitten story of a young girl thrown into the most vicious web of carnality ever imagined... a woman's prison.'

Back cover:
“I’ve never done this before with a woman,” she cried, lifting her face toward the inviting leer on her cellmates face. “Suppose one of the guards finds us together?”
The other girl’s leer broke into a knowing grin. “Don’t worry about them, honey. It’s keeping them out of our little parties that’s more of a problem than being caught!”

Inside:

Ginger lay there in the dark, her heart pounding, a strange, exciting feeling beginning to seep all through her as she listened to the sounds in the dark below her. She heard Lila whisper: “There, that’s better, darling. I don’t like to have even that old nightgown of yours between us.
Then Maureen whimpered: “No! No! Please don’t. Not tonight, please!”
“I can’t help it, hon. Just for a moment. Your breasts are so cute and warm and firm. Ahhh!”
Then there was silence for a few moments, except for the sound of increasingly heavy breathing. Then Maureen made a faint, muffled outcry and Lila giggled, and said: “There! I knew you’d like this. Want me to keep it up?”
Maureen practically groaned it: “Oh, yes! Yes!”