Here's why:
* Common nouns are general names for people, places, things, or ideas (e.g., dog, city, book, happiness).
* Pronouns replace nouns to avoid repetition (e.g., he, she, it, they).
* Possessive pronouns show ownership or possession (e.g., her, his, their, ours).
"Her" indicates possession or ownership, making it a possessive pronoun rather than a common noun.