Well obviously they weren’t practicing safe sex.
How about if she is unfulfilled? Can she go out and get some strange, as long as she cooks dinner, does the laundry and is a good mom?
With regard to the incident I reported in Comment 13, where the husband was unfaithful during 4 months in Europe, this is what happened. The wife said she could understand how he felt a great need after several months away. However, the wife said she might have a great need some day, and if she acted on it, then it was one her husband owed her. In fact I think something like that happened a few years later, but they stayed married.