Yes. This is a reflexive pronoun. Its antecedent is the subject of the gerund phrase "her talking to herself." "Her" is the subject (even though it is not the subjective form) and "talking" is the gerund (a verb functioning as a noun). The phrase is also the object of the preposition "to." (Which is why the objective pronoun "her" is used.)
The only function of an intensive pronoun is to intensify or emphasize a noun or pronoun already in the sentence.
The sentence "We listened to her as she was talking to herself" is awkward and has inconsistent tense. It should be "We listened to her as she talked to herself."
Hope this helps.
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