Ayn Rand identified a woman's essential characteristics the same way she identified those of man, by careful observation of reality. For example, she wrote that "The Objectivist ethics proudly advocates and upholds rational selfishness -- which means: the values required for man's survival qua man" (The Virtue of Selfishness, p. 34). Now some collectivist could attack her by saying that she provides no support for such a statement. Where, the adversary might argue, is her explicit support for such a claim? Where are the quantifiers, the stastistical data, the case studies? In the absence of such support, must we reject Ayn Rand's view of man's nature? I think not.
But Objectivism does provide an explicit support of this claim - Peikoff does so in OPAR, wherein he builds the philosophy from the ground up, explicitly, and I do not recall any discussion of masculinity or femininity therein.
Further, to demand explanation is the essence of reason. There are precious few things to which you can point to say "see, it's self-evident." Human behavior is not one of them. That most women behave a certain way does not say anything about the nature of femininity.
Obviously your experiences lead you to conclusions different from Ayn Rand's and mine. It doesn't hurt my feelings that you disagree with Ayn Rand on this matter. On the other hand, I have no intention of overthrowing my own conclusions just because you can't see things my way.
If your experiences and mine have lead us to different, contradictory conclusions, it follows that there is something wrong with one or both of our interpretations of these experiences, since the world is what it is and doesn't vary from observer to observer. I'm not asking you to overthrow your conclusions, I'm asking you to convince me of their validity.
Finally, the topic of the 'closed' nature of Objectivism is one for a different thread, but Rand did not want her name used to promote her philosophy, out of concern that her writings would be taken as the dogmatic, definitive statement of the philosophy.