Identifica el complemento indirecto. pablo neruda dedicó un poema a la señora.

"Señora" is the indirect object.

So, we cant replace the indirect object with a indirect object pronoun:

Pablo Neruda le dedicó un poema.

In Spanish it is possible to use at the same time the indirect object and the pronoun that was to replace it. This is called redundancy and is used a lot in the Spanish language.

Pablo Neruda le dedicó un poema a la Señora.

Pablo Neruda dedicated a poem to the Lady.

Explanation:

In grammatical terms, a direct object of a verb is a noun or a pronoun that is being directly acted upon by a person or thing by way of a verb.

On the other hand,  the indirect objects, are noun phrases that indicate to whom or for whom an action is done.

In the sentence above, the direct object is the poem, and the indirect object is the person to whom the poem is dedicated. La señora.