Evolutionary psychology: -Rone men and -None Men

Women do settle down with the provider/protector ‘rone’ type. During ovulation, a womans sense of smell becomes more sharp than other times of the cycle and are driven in general toward men who have better compatibility to them with non similar MHC immune genes. They also prefer men during that time who are more symmetrical and fit and masculine, and I believe androstenone is the signal for symmetry/fitness. The scent of androstenone becomes more pleasant to those women during ovulation who find it urinous/negative smelling normally

It has been shown that as a couple has more similar MHC genes, the womans sexual responsiveness to her partner decreased and had more sexual fantasies and infidelity around ovulation. More on this herel. As mentioned there also, if a women changes her birth control status during the relationship, that too can change the MHC preference and therefore cause these kind of issues. If sex is not occuring much then this can be a possible indicator.

So if she chose or now has a partner who isnt very symmetrical/fit (or using androstenone regularly during ovulation) or much more importantly a partner has too similar MHC immune genes (or changes her birth control during the relationship), then yes its possible for this scenario to occur.