Based on a Naaleh.com shiur by Rabbi Shimon Isaacson
There is a disagreement among the Rishonim whether havdalah is d’orayta or d’rabbanan. The majority of Rishonim rule that it is d’orayta. Are woman obligated in havdalah? Is havdalah a mitzvah of Shabbat or of motzai Shabbat?
Since women are obligated in the negative commandments of shamor, they are also obligated in the positive commandments of zachor. According to the Rambam, havdalah is part of the mitzvah of Kiddush and women are obligated. According to the Orchot Chaim, women are only obligated in kiddush. Havdalah is a time bound mitzvah of motzai Shabbat from which woman are exempt. Based on this, the Rama rules that women should not make Havdalah for themselves.
Some Rishonim argue that although havdalah is d’rabbanan, women are still obligated because it was meant by the sages to be a part of the mitzvah of kiddush. The Mishna Berura cites the Bach who asks, if the Orchot Chaim is correct and woman aren’t obligated why can’t they make Havdalah anyway? In fact the Magen Avraham and the Bach rule that women can make havdalah. How then do we understand the Rama?
With havdalah there’s no maaseh (action). The blessing itself is the mitzvah. Therefore the Rama rules that women shouldn’t say it. Preferably, a man should intend to recite it for a woman when he says havdala for himself. The man should not say havdalah earlier because if in fact a woman isn’t obligated, he may be reciting it in vain. In principle, a woman is obligated and therefore if there’s no man the woman should say it herself.
The Biur Halacha questions whether a woman should say the blessing of Bori meorei haish since it is essentially a mitzvah of motzai Shabbat which women aren’t obligated in. Therefore, it may be an interruption between Borei Pri Hagefen and Havdalah. The common practice is that women do say Borei meorei haish.
There’s a Kabbalisticsource that mentions that women shouldn’t drink the wine of havdalah. Rav Meltzer explains that Borei meorei ha’aish may qualify as an interruption before Borei pri hagefen. Therefore, a woman shouldn’t drink the wine. However, the custom is that if she makes Havdalah for herself, she does drink from it.