The girls prepared themselves a complete meal.
pronoun:

antecedent:

Pronouns are used to refer back to the subject in order to avoid repetitions. Antecedent is the word or words that come before the pronouns. If the antecedent is singular, the pronoun used should also be in singular form. Same goes with using plural forms. Therefore, the antecedent in this sentence is "girls" and the pronoun used is "themselves".