And concerning the female lamas, there are hints that there were many more spiritually advanced women in earlier times than we know nowadays by name. So maybe on the one hand, advanced female practitioners didn't gather as many students around them as men on a similar spiritual level. On the other hand, it seems plausible that women are also underrepresented in the historical recordings, since they lived outside of the official institutions. Lama Ole Nydahl says that under his students which he sends out to teach and to run the centers, there are as many women as men. In principle there is no difference in the Diamond Way.
Women have exactly the same possibilities to make good progress.
The reason, why men are still dominant in some western buddhist institutions lies partially in relicts from Tibet's monastical culture, which have nothing to do with Diamond Way Buddhism itself. Another reason are hierarchical structures. Although men seemingly like to build up these hierarchical systems, to women it does no good to live in such a climate. They work better in open round meetings than from the top to the bottom. And women can also be strong without having to be stronger.