Often, the woman doesn’t say it because the person saying kiddush or havdalah has everyone (other men and women included) in mind, ie. he is being the shaliach for all of them.

But, if a woman didn’t hear kiddush or havdalah from someone else, or that person didn’t have her in mind, then she is halachically required (just as much as a man) to say it for herself.

Some people think that since the mitzwah of kiddush or havdallah is a time-bound mitzwah, then a woman isn’t obligated by it. But, mitzwoth pertaining to Shabbath don’t fall into this category because the mitzwoth of Shabbath involve and intimate mix of positive and negative commandments; and since the woman is required to keep the negative commandments–even those bound to time–in the case of shabbath this brings with it the requirement to keep the positive mitzwoth of shabbath as well.

again *consult a Rabbi for exactly how this all plays out*, but in short since a woman has an obligation to say havdalah and kiddush, she can also say kiddush/havdalah for men as well.

Since the mother has no halachic obligation to perform the brit milah, her performing the brit milah would mean that the child/father/beit din would still need to perform a brit milah (or at least draw a drop of blood representing the milah — as is the practice in the case of someone who is incidentally already circumcised (like a convert, someone circumcised by someone with no mitzwah obligation, or a baby born naturally circumcised–which does happen)) at a later time.

Similarly, a non-jew, or a child, can’t perform the brit milah because they too are not obligated in the mitzwah.

That’s as far as performing the mitzwah one self. As to appointing a woman shaliach to perform the mitzwah on one’s behalf–I don’t think halachah recognizes women as shlichim—but I’m not a Rabbi, nor do I have the requisite knowledge.

Let’s just leave it at there’s more to it than just minhag — as opposed to other feminist issues like female sofrot.

Also, you copied the quoted paragraphs twice..

And lastly, There’s another aspect of traditional brit milah that might raise eyebrows (well, raise them even more) w/ a female mohelet.