Correct answer:
me
Me is the indirect object pronoun that matches the first person singular. An Indirect Object Pronoun is a person that, in indirect way, takes the action of a verb. So this tells us to whom or for whom an action is done. On the other hand, prestó is the conjugation of the verb prestar for the third person singular in the preterite tense. Therefore, this sentence is given in the past. Finally:
Mariana: Es muy generosa. Ayer me prestó prestó dinero
