If her fantasy had gone further to being masturbated to orgasm that would have been unrealMy first wife had a fantasy that would fit this. She fantasied about being a live sexual demonstration model. She would be naked there would be a tutor and a room full of students, like in a lecture theartre. The tutor would point out all of her "rude" bits, touch them and manipulate them while explaining their nature and function to the students. He would have her take a variety of poses, mainly displaying her cunt, opening the pussy lips thrusting his fingers in, again while explaining to the students. She remains passive throughout the fantasy, having no control over what was happening. She wasn't masturbated in front of the crowd, just displayed.
In real life, she did enjoy having people watch us fucking. When we started out swinging we started with making out in front of other couples, while we watched them. She loved that, more so than the swapping we got into later. I think the activity fed the same fantasy outlined above.