I've been poring over the big papers (most cited journal articles) regarding modern sexual behavior and attitudes towards sex. While promiscuity is generally correlated with infidelity, so are particular big five personality traits and styles of attachment. Women who generally cheat are typically high in neuroticism, low in agreeableness and in conscientiousness. Promiscuous behavior tends to be correlated with extroversion, but I don't think it was highly correlated with anything else, which was odd because promiscuity is moderately correlated with infidelity. I don't have the study on hand. Promiscuity is also correlated with particular attachment styles. I'll update this when I have my notes, but these things might be better explanatory factors for infidelity than promiscuity, though we shouldn't ignore the relationship between an unrestricted SOI (closest scientific proxy to promiscuity/ high n-count) and infidelity.