Ask her to turn around while you finish

"Okay, " I said, "but maybe you could turn around while I do so."

I figured pretending to be embarrassed was the best approach. She nodded her head and slowly turned around, peeking over her shoulder one last time before facing away. I noticed she was wearing a short black skirt and a racer-back tank top, that showed her angular shoulder blades. Alison was thin, but that still had nice curving hips and a shapely ass.

I imagined lifting up that skirt and fondling her ass as I began to stroke myself slowly. She heard the sounds as I began and slightly lowered her head.

"Mmm. Sounds like you're enjoying yourself," she teased me and I knew she was turned on by it.

Not coincidentally, she turned toward the television, which continued to show the threesome in action. A very buxom blond laid back and fondled her tits as a brunette kissed her and then slid down to lick her pussy. The blond was clearly enjoying it, and so was Alison.