Right answer:
Se la dio Florencia
This sentence is a case of indirect object pronouns and direct object pronouns working together. The purpose of the indirect object pronoun is to tell you to whom or for whom something is done. So this action is being performed for Marcela, and the indirect object in this case is le. Since indirect object pronouns and direct object pronouns are working together le changes to se. On the other hand, a direct object pronoun replaces a direct object, that is a noun that directly receives the action of a verb in a sentence. So la pelota is the direct object and la is the direct object pronoun in this case. Finally:
Se la dio Florencia