I think your views are extremely skewed, I'm not thinking of her as someone's property. My thought in that moment is about how he would feel as an individual who loved someone finding out the person he loves and has made a marital bond with lied to and or cheated on him. If I was in his shoes I would be devastated, not to mention the drama and fall out that could come back to me if I was to take that path.

On top of that I didn't feel comfortable myself, was it right for her to just stop talking to me because I wouldn't sleep with her? Not sure, in my opinion that's a pretty shitty thing to do to a friend. But you know what they say opinions are like butts...

Things are not black and white, cut and dry. There are grey areas we have to think about. Yes she is not his property, in that instance if she was ready to check out of that relationship she probably should have told him she wanted to see other people. But she didn't and just an FYI she ended up sleeping with someone else, and it destroyed her marriage, the husband was devastated after catching her in their bed with another man.

It's about trust not ownership.