I researched today. A woman "laying with" any man she is not married to was a sin punishable by death of the woman. Now you mentioned that the sin seems to be contingent on marriage, if there was no marriage planned it seemed to you there is no sin.
It's possible that is the truth, there is no mention of the man sin unless he "lay with" another mans property (betrothed, wife, handmaiden). Women were typically betrothed by 3 yrs old and Married by 14yrs at the latest (as soon as they were able to bare children). Men would be considerably older.
Mary was between 10 & 14, Joseph was 99yr old. So if you are engaged by 3 and if a women is divorced, laying with a new man is a sin, and give to the closest male relative as wife if her husband dies, it would be hard to for a woman not to sin having sex outside of marriage, oh and of course if she were not a virgin on her wedding day it was a sin punishable by stoning to death.
Now whoring was a profession, a dirty profession of those who never got a husband or dead husband didn't have living male relatives or a woman who was defiled by rape ( she would not be put to death but would be unclean and not marriage material).
Whores were looked down on but not put to death, they were not owned by any man but were considered temptresses, dirty, temptresses. No where does it say to go to a whore is a sin, so you maybe right. It's frowned on but not a punishable offense. Same with husband, woman could have one husband but man often married many women.
In the New Testament man seems to be addressed more than woman. Fortification is used to describe a sin against God, but it's not truly described. If it is a description of all the sins of sexual nature described; then it's sex with a man owned by another man, beast, a man or a woman related to you or anyone you have slept with.
Woman must still remain chaste til married and the only their husband, even if divorced. Now the word "whoremongers" pops up and are considered sinners, a man who sleeps with unclean women a lot but not because he slept with one.
Exodus 22:16 says that if a man lies with an unbetrothed woman he should marry her. Paul talks about remaining pure and not marrying bc that distracts you from God but if your not able to control yourself, marry because it's better to marry than sin.