When x-linked traits are recessive, females will express the traits only if they are OFFSPRINGS OF FEMALE CARRIERS AND AFFECTED MALES for the recessive allele.
Because females have 2 x-chromosomes, when recessive x-link trait is present it is not manifested in the female but she is a carrier. The only time that the x-link trait is manifested in a female is when she is the product of the female carrier and the affected male.