Hi Saadat,

 Sorry for the late reply. I haven't checked this site in a while. As the author of this article, I'm really gratified that people are still reading it.  To answer your question, I don't know why there is not a female equivalent of the hijras ( or female eunuchs as you call them). However, there was a case in Pakistan recently (about two years ago), where one of the partners in a married couple was found to be a female to male transexual, I think his name was Shumyl. So the situation does exist, but not to the extent of hijras.