That's because you're normal. Who made the rule: Men or women, 4 young kids, thou will not have time to cheat? No such rule exists.Doesn't she have 4 young kids, one a baby still being breastfed? Is she that lascivious that she had the energy for such a thing?
If it did. Then we'd all be having 4 kids because then our marriages all would be rock solid!