Men are obligated to count the 'Omer every night with a Berakha ([Bracha] blessing), provided, of course, they did not miss one day completely. Concerning women, however, there is a difference of opinion.
Since this is a Miswath 'Aseh Shehazzeman Geramma (a positive commandment dependent upon time), women, according to all opinions are exempt from this commandment. The question is, however, does "exempt" mean that they should not do it, or does it mean that even though they are exempt, if they wish they can count the 'Omer with a Berakha?
Ashkenazim generally follow the latter opinion, which was brought down by Rabbenu Tam, and permit a woman to count with a blessing. Though it should be noted that there are Ashkenazi Posqim who disagree with this. As such, each person should check with their own Rabbi.
Sephardim generally follow the opinion that women should not count the 'Omer. Rabbenu the Hida, o.b.m, says that if a woman has the custom of following Rabbenu Tam in other Miswoth, such as shaking the Lulab, then she can count the 'Omer. The Ben ish Hai, however, says that even in such a case, she should not recite the blessing.
Orah Hayyim, Hilkhoth Sefirath Ha'Omer, Oth Yod Teth)
