‘Her’ is a pronoun. Specifically, it is a possessive pronoun, which means it is used to show ownership or possession.
For example, in the sentence ‘That is her book,’ the word ‘her’ indicates that the book belongs to her. Possessive pronouns like ‘her’ replace nouns to avoid repetition and simplify sentences. Other examples of possessive pronouns include ‘my,’ ‘his,’ ‘their,’ and ‘its.’