In the sentence, "Blank" is the antecedent that agrees with the pronoun "her."
In the sentence "Blank is best known for her oatmeal cookies," the pronoun "her" refers to a female antecedent. However, since the sentence already has a blank, we cannot determine the specific antecedent without more context. Without knowing the name or identity of the individual being referred to as "Blank," we cannot select a correct answer.