Dear JAHB Readers Should A Relationship Be This Open?

My girlfriend and I were talking about how a relationship should be as open as possible to both parties and in presenting her view, she told the following story; A married lady met a married man (a pastor) on a visiting trip to another country. One way or the other they got talking as their seats were next to each other and eventually exchanged contacts upon arrival. Moving on, the man later invited the lady out for lunch on a date that was meant to be just casual or something like that. In the course of the lunch, the man started 'waxing lyrical' on how he's developed feelings for her and would really like it to be mutual and all. According to the story, while the lady didn't accede to the proposal, she also didn't express her declination in very strong terms but rather chose to explain how it is that they are both married and that such a proposal can't work out. (I wouldn't know if she was respecting the station of the man hence the rather mild nature of her response). Moving further, they departed on casual notes, and shortly afterwards, the lady headed back to her home and hubby. She was said to have later relieved the experience to her husband (with no drama taking place). However, and according to the story, it made the couple 'realize the need for a re-bonding period of sort'. (Note that there was no reported perception of a threat according to the story told which I believe gives the story a loophole). Anyways...back to me and my girlfriend.....She believes that the wife did well to tell her hubby about the incident especially in the light of being open in a relationship, and says it is the kind of mindset she desires for the level of openness she wants for our relationship. I don't find anything wrong with that but I believe there could be a more deeper problem here - a married lady going for a casual lunch with another married man without the spouses of either in the know isn't even appropriate to start with! Furthermore, I believe the married lady in question went too far (even if ignorantly as the story is made to sound), however she had the option of strongly expressing how she felt about the pastor's proposal. I am not saying someone isn't prone to make mistakes however I consider that sort (a pre-planned incident) not a mistake. If it happens, I believe someone needs to carry out a thorough soul search. Rather late and happy than remaining miserable and unhappy in a union for ever. To truly respect the sanctity of what one shares with one's spouse is to know to observe such boundaries. My girlfriend, in the course of our back and forth on the issue, further mentioned that 'these things do happen' and so one needs be realistic by ensuring that such levels of openness is maintained at all times. I totally disagree with the principles/rationale expressed on the issue by my girlfriend's due to the fact that it tends to generally lower certain expectations about how partners should conduct themselves in a relationship and much more in marraige. I would however like to get as many views as possible from you guys on here. Gracias!