the woman knew she didn't have a marriage. It was not because there was no paper signed or rabbi that officiated at a marriage. But there was this lacking---a public declaration of intention where the two let the community at large know that they were a couple. They had not dignified their union in such a customary way and the children would not have the protection and recognition that came with such a public statement.
While I am sure your friend's situation is entirely accurate, dear NaC (and peace to you!)... I am not sure that what you've stated above is entirely correct. First, one way this woman and her man could have lived together without being married would be if she were his concubine (which was acceptable under Jewish tradition). And although not a "wife," traditionally the children of a concubine had some rights. And she could have been a concubine simply by reason of the man actually already having a wife (or wives), with whom she (the woman) did not live. Indeed, she could have been a wife's maidservant. If that were the case, the community wouldn't have really had a problem with her relationship... unless, of course, the wife had one. However, again, although she would "have" the man... he wouldn't have been her husband. Or... she simply could have been a concubine.
Secondly, though, the issue here was not that the woman had a man who wasn't her husband. The issue is that when asked about her "husband" she didn't LIE:
"[Jesus] said to her, "Go, call your husband, and come here." The woman answered and said, "I have no husband." [Jesus] said to her, "You have well said, 'I have no husband,' for you have had five husbands, and the one whom you now have is not your husband; in that you spoke truly."... the hour is coming, and now is, when the true worshipers will worship the Father in spirit and truth; for the Father is seeking such to worship Him. God is a Spirit, and those who worship Him must worship in spirit and truth."
Concubine or not, however, this woman was having a somewhat covert relationship, one where the man didn't actually live with her (or she with him, as she would have run and called him once my Lord revealed that he knew they weren't "married" - she didn't run to get the man, however, but the "men" in the city)... and so would have replied to ANYONE who asked her that she had no husband. Because (1) this was the TRUTH and (2) she didn't want anyone to know she was seeing the man. What makes it a sublime truth, however, is that no one else KNEW about her and the man... except my Lord. Otherwise, she would have replied, "The man I am with is not my husband." Which would have also been a truthful statement. But her statement was to indicate that there was no man.
However, rather than leave the matter at her truthful response of "I do not have a husband," my Lord was merciful and let her know that while, yes, it was true that she did not have a HUSBAND... HE knew she actually DID have a man (anyone else asking her would have received the same reply and so wouldn't have known anything to the contrary). AND that she had actually had 5 husbands before him... something else others did not know about her.
Which is why she marveled and perceived him to be prophet: he knew things about her that NO ONE else knew. For if others HAD known about the man they would have concluded that either (1) he WAS her husband... and so they were okay... (2) she was HIS concubine... and so they were okay... or (3) they were adulterers, which was NOT okay and most likely would have resulted in a stoning or something close. Because at that time, there really was no other "situation" where a woman could publicly have a non-platonic relationship with a man. Heck, if you really read the scenario, a woman couldn't even SPEAK to a man to whom she wasn't married... publicly or, even as the account suggests, otherwise. (John 4:27).
I hope this helps and, again, I bid you peace!
A slave of Christ,
SA