The family has awesome and still somewhat mysterious power to shape our lives and view of reality. There is literally tons of in-depth research going back to at least the seventies --- which is not to say that one must be a slave to family history, its just something that should be borne in mind.
There are several factors involved: What is the girl's birth order, for example? Whether one is a first born, second born, third born, or fourth born seems to be a factor. We can't go into it here, but if the child is a first-born, she/he tends to identify with the father -- there are sociological/historical reasons behind the development of a patriarchal society.
Second-borns tend to identify more with the mother, for the same reasons. Third children tend to be concerned with the relationship between the two heads of household. Fourth children tend to be more concerned with the unity of the family, etc. And so on and so forth
Now, if the young woman is a first child, I would informally predict that her natural tendency would not be to cheat (as her first-born status would identify her with the father, providing he does not "cheat"), this would be so, I think, despite the fact that she spends much more time with her mother. If she is a second-born (placing her in identification with her mother), I would informally predict that her first tendency would be to "cheat."
Third and fourths, I do not know. I am not an expert in family therapy.