Per Miridan's post, you being paranoid is just
one of the checks.
If your spouse is lustful or seducer, this will also trigger regardless of you're paranoid or not - presumably because you have good cause to suspicious.
If your spouse is not lustful and not a seducer, the event triggering means they actually cheated and the game is just giving you a chance to prove it.
All together this means you will not see the event if
ALL of the following is true:
- You are not paranoid.
- Your spouse is not lustful or seducer.
- Your spouse is faithful.
As for the last point. Highly Honorable (per their personality type) spouses will generally not readily cheat. Soulmates will not generally cheat. Chaste will not generally cheat. So if you don't want to this event spammed don't marry obvious floozies and don't be paranoid.
If you hate it and basically never want to see it, in addition make sure your spouse is honorable or your soulmate (not just non-lustful). As if you've got a bunch lustful hunks running around, ordinary women just won't be able to resist.
IIRC, there's still a small handful of edge-case events that bypass those precautions, as they relate to events generated by lustful courtiers. However these aren't constant. So doing the above you should be able to go entire lifetimes, even multiple without seeing it.