-There are varying opinions amongst the Poskim regarding if women should/may count the sefirah with a Bracha.
Women are not obligated in Sefiras HaOmer, as it is a “Mitzvas Asei SheHazman Gerama, a Mitzvah that is bound to a certain time-period.”
The Mogen Avraham maintains that women have accepted this Mitzvah upon themselves as if it is an “obligation” and thus they must indeed count with a Bracha. (Quoted in Mishna Berura 489:3)
The custom of women in Europe in the time and place of the Chofetz Chaim was not to count Sefirah. (Mishna Berura ibid.)
The Shulchan Shlomo (quoted in Mishna Berura ibid.) maintains that women should count the days, but should not recite the Bracha before the counting. His reasoning is that women will all but surely forget to count at least one of the nights (as the reason many men don’t forget is that they go to Shul for maariv. Men who do not attend Shul for maariv, according to this opinion, should probably also not count sefirah with a Bracha, as they too will end up “messing up”)
Today’s days many women do indeed have the custom to count Sefirah with a Bracha, as today we have Sefirah calendars and other reminders (including many email, and text message reminders) that make it more likely that they will indeed complete the entire 49 day count. (See Aruch HaShulchan 489:4 that women should count with a Bracha as they do other Mitzvos Asei Shehazman Gerama.)
-If a woman indeed wants to count, it is important that she at least know the basic meaning of the words being said (i.e. how the days and weeks being said in Hebrew translate into the appropriate day of the counting.) (See Mishna Berura 489:5, Shu”t MaHaril Diskin Kunteres Achron Siman 5 Os 55)
Women who follow the Sephardic traditions do not recite blessings on any Mitzvos Asei SheHazman Gerama, and thus should not recite the Bracha on Sefirah.
As with all matters of Halacha, a Rav should be consulted for Halacha L’ma’aseh.