It didn't feel as though you were trying to help her understand but rather to force your opinion over her. You offended her and then insulted her intellect, well done! I think you need to do some work on your delivery, then people might be more inclined to listen to you.
Personally I feel similar to smalltowngirl in that outwardly I appear feminine and I like to dress and act feminine but I think more like a man and in some ways I identify more with men because we think similarly. My best friend is straight and male and I feel more like one of the boys than one of the girls. I like maths and science and talking about bikes and cars etc.
My sister takes this further and is more polar than I am, she is far more feminine and dresses and acts more feminine. She loves make up and clothes and she is very trendy. Although she is also extremely confident and dominant which sometimes makes her appear more masculine as those qualities or at least how she expresses them are not often found in women and a lot of her friends call her a man not because she looks like one, far from it, but she definitely thinks like one. She however is straight and has no interest in women as I have no interest in men.
So fair enough environmental factors have obviously contributed to why we are as we are, because we were brought up in similar circumstances but it doesn't explain the difference in our sexuality and further more we have a half sister who also displays similar characteristics but is older and grew up on the other side of the world to where we were, without our common parent.
My sister has more knowledge on this subject than I do, as she did psychology funny enough at Hull university, but we both have a similar opinion in thinking that its the concentration of different hormones during pregnancy and while growing up that probably has a lot to do with the differences between us and other female bodied women. Apart from dna, human foetuses are the same until hormones are released which account for our biological differences. Our theory could be wrong and perhaps its because we were born and conceived in an area with high levels of ddt in the ground, which had some kind of influence over our development. Obviously we lean more to the scientific approach, but we don't know for sure and to say there is one definitive theory that explains it all is wrong. Theories are opinions until proven otherwise and I think we still have a way to go before we can explain many of the complexities on an individual basis.
I read a synopsis of the book you suggested and it sounds interesting and I think I would enjoy reading it. My initial take on it, is that if gender and sex are socially constructed then surely the outcome is dependent on the experiences of the individual. I obviously have to read it more in depth and get back to you whether it changes any of my current opinions.