The reason more women don't buy Iron Heart is simple -- the jeans aren't marketed to them ! And it's kinda tricky, because if the jeans were billed as unisex (American Apparel style), that may turn the bread-n-butter macho-motorcycle-men buyers off. I dunno though...seems like the men on this board are totally supportive of their jeans being worn by women !
Definitely, having some female models on your website, wearing IH proudly, would help a lot.
Understand, however, that many women just don't have the physique for Iron Heart. For instance, though JLo is hot, she'll have a tough time squeezin' into a properly sized pair of IHs. On the other hand, Madonna would probably look fabulous in a pair.