Carla by Toni Stevens

Rear cover blurb: 'Carla is a grey-eyed beauty. The sort of girl most men fall for. But Carla isn't interested in men. Carla likes women and they know it! Margaret knows because she is the first girl to be seduced by Carla. Sorrel knows because she is the sadistic one who takes Carla by force. Marcia knows because she cannot have enough of Carla's experienced lovemaking. And Jamie knows, because she is the girl Carla yearns for to fulfil her needs'

Inside:

Carla Manning paced the empty and quiet apartment, her eyes darting to the wall clock incessantly. She puffed on a filter cigarette in an agitated manner, her slender hands occasionally brushing back her loose black hair. It was close to midnight and yet sleep was unthinkable as long as she was alone in the apartment and had to endure depression alternating with unrest.
I’ll bet she’s kissing him right now, Carla thought, standing by the window and hugging her arms to her small firm breasts. Parked on some dark street, probably necking like two high-school kids. She’s doubtless even allowing him to pet her, and he’s asking her to move into the back seat where they can have more room.
Carla shuddered and frowned, touching her forehead to the cool glass of the window. What’s the matter with me, she thought. Why on earth should it matter so to me what she does? Why does it make me feel sick inside just to think of her letting a man put his hands on her body? Why do I become so upset when she goes out on a date? Why do I worry so about her?