The game never explicitly notifies you of infidelity. No "Cheater!" popup, no relationship panel flag. You must infer from behavioral cues.
| Behavior | What It Suggests |
|---|---|
| Frequent "Flirt," "Kiss," "Make Out" with non-partner | Active romantic pursuit |
| Late-night visits / "Go Home" ignored | Secret rendezvous |
| Partner's Relationship Bar dropping rapidly | Neglect + rival gains |
| Moodlets: "Guilty," "Nervous," "Flustered" after socials | Internal conflict (base game + expansions) |
| "Dirty Laundry" memory (if caught by another Sim) | Gossip system triggered |
Remember: Some Sims are naturally flirty (Romance Aspiration, "Flirty" trait). Context matters. SimPE is the only 100% proof on PC.