I would begin by asking what she saw or heard that lead her to suspect cheating. How does he treat her? Has anything changed in the relationship? Can she get a hold of him when he is out of town and if so, how does he respond to her? Is it usual for him to go out of town on business and if so for how long?

Having an affair requires communication, so look at his cell phone for questionable phone numbers. Look at credit card receipts for restaurants with high charges or other purchases.

If her feelings are really strong that an affair is likely happening, she needs time and patience to find the proof without alerting him.

If after time, she is unable to find anything, she may want to talk to him about her concern. She should listen carefully to his response. Is he dismissive, gets angry, says she’s crazy, puts her down or is he supportive and reassuring that he’s not looking for a relationship with another women.

Feelings generally don’t go overnight and our intuition is peeked for a reason. She may want to keep her ears and eyes open and pay attention to what he tells her and examine how the relationship is going.