Sofistry

Livia wasn't convinced. She knew Tony of old. Sure, he was a bully and had beaten her viciously back when she was playing him and Terry. But she also knew that when it came to women and sex, Tony was a shy guy and most unlikely to make the running.

She was pretty certain Sofia and Tony had been doing it, regularly... as a weekend activity of which Marcia was unaware... or knew about and didn't care. Livia was pretty sure Sofia would have initiated it, probably just for the hell of it.

So maybe the sisters weren't so close.