@bigneil you need to think "bigger"
You commentary seems to be coming from a scarcity mindset.
If a female is going to"do the exact opposite" of the boundary you communicated, that female is not only immature, but is already resentful, and definitely does NOT have your, or the relationships, best interest at heart. She needs to be dropped hard, and quickly.
Setting boundaries in a relationship, while inclusive of behavior around the opposite sex, has MUCH more to do than simply trying to " keep someone from straying"....
It has to do with how you treat the other person as a whole, how you treat the relationship, how much value you show for the relationship, addressing the other person's needs, not being disrespectful, etc.
If you are solely working your boundaries from a place of keeping her from cheating, you've already lost, in a big way.