Men are born sexual .
Unless the woman is a lot older, it will not work.
If my partner was seeing another woman friend without me, and same age group...of course!!! I would worry....In fact 'why' has he a need for another woman, in his life.That stuff should stop, the very day he said 'I do'.
Men should not seek the friendship of another woman his own age, if he has a wife..or even a partner.
The very same for a woman: If they are partners, not married it really should be a part of their respect for each other.
Certainly it would not give the partner left alone a feeling of confidence,about that relationship.