There's no way to completely parse out what is nature and what is "nurture" and certainly hormones do play a part in things, but also not to the extent that most people think they do. I'm not discounting your friend's personal experiences but there is also something to be said for how our expectations and the other elements of the environment play a part.
Check out this excellent story for a short version and the book Testosterone Rex for more.
But also, within some species—including our own, as this chapter fleshes out some more—neither sex has the monopoly on characteristics like competitiveness, promiscuity, choosiness, and parental care. The particular pattern, as we saw, depends on the animal’s ecological, material, and social situation. This suggests that, even within a particular species, the effect of the genetic and hormonal facets of sex on brain and behavior must not inflexibly inscribe or “hardwire” particular behavioral profiles or predispositions into the brain; not even those more common in one sex than the other. Instead, they are drawn out to a greater or lesser degree, as circumstances dictate.
Fine, Cordelia. Testosterone Rex: Myths of Sex, Science, and Society (p. 87). W. W. Norton & Company. Kindle Edition.
