TasteOfHoney, let me offer another example to better illustrate the "optional plural" and its intent to refer to "one or more":
In the AT&T SW, on p.3 and in section 2, you'll find the phrase "This information is believed to be imperative in locating a suspect(s)..."
This is coming from the same source (MPD) as the other SW which used the term "relationship(s)." The MPD clearly wants to express that they're looking for one or more suspects. They don't know how many suspects are involved. So they want to give themselves some wiggle room that there might be just one suspect, or there might be more than one. So better to phrase it as they did, instead of saying, "locating a suspect."
Same thing with the prior "relationship(s)". They were aware of one, and they mentioned it specifically - the conversations with CW that began in January and continued up until MB's death and turned flirty and familiar and intimate in nature. But at that early point in the investigation, they didn't know what else they were going to uncover. So rather than paint themselves into a corner and mislead someone into thinking there had been a singular external relationship to the marriage, they put the optional plural in there.
Did MB have more than one external relationship? We have nothing to indicate that she did. But we can discuss the one that we do know of, although it would be unfair to speculate that it was physical as there is no evidence to support that. Do I judge or shame Missy for the relationship with CW? Absolutely not. And what is considered "flirty, familiar, intimate" has a wide latitude of subjectivity, so it might not be nearly as intimate to us as it might have been to LE who read it.
But bottom line, we have documentation of some kind of relationship on MB's behalf, and the speculation isn't to judge her but to figure out if the murder was somehow connected. That's fair to do. What isn't fair, IMHO, is to accuse her husband of indiscretions that have no basis whatsoever that we know of, other than local rumor mill. And there is nothing more untrustworthy than a local rumor mill. MHO.