Dallasguy,
First of, I am very sorry for what happened. I am no expert in this field but here is what I think. In my opinion, the relationship has already come to its inevitable end. You are trying to hold on to it because of the good memories. You aren't being able to let go. So you are trying to cover it with the 'honesty" card. If you hold on any longer, it is going to be a disaster for you both.
Regarding the comparision between you sleeping with hookers and her sleeping with a friend, I think it's not the same. It would be the same if she paid for sex too. Then you could accept that she has emotions only for you. But, just because a guy talked nice to her, I mean come on, how many guys are going to be nice to a lady, 10000? So ....? Her "fling" had a emotional undertone. If she had strong feelings for you, she would never loosen the emotional grip.
Don't buy the honesty card. Her honesty makes her a good person. We respect her for that. But, it's not a justification for what has been done.