Is "her" a "possessive pronoun" or an "object pronoun"?

No, the mistake is in the second one. "Her" there is a possessive adjective.

So, to answer to your question, YES, that word can work either as an object pronoun or as a possessive adjective.

Which wouldn't be a problem to accept if you think of words like "have" or "do", which in some instances work as an auxiliary and in others, as a verb.

To clarify about the possessive pronoun, it is "hers", like in "She was driving hers" (you can see it is a pronoun because it substitutes "her car").

Well, it is an object pronoun in the first sentence. You're right.

However, in the second sentence, 'her' is a possessive adjective, not a pronoun. The possessive pronoun would be 'hers.'

yes. Try finding a list of pronouns in English.

About.com probably has it. Or just search "English pronouns", and see what comes up.

You are correct.

Nominative to vocative all eight cases are applicable to pronouns but in I person and third person, vocative will not be there.

1.she

2.her

3.her with a preceding preposition 'of'

4. -do- 'to'

5. -do- 'from'

6. her as well as hers.

7.her with a preceding preposition 'in.

Her is a possessive pronoun.

Tou are right. It can be both. The exact meaning will depend upon the context.

Yes.

ITS BOTH, UNLIKE HIM/HIS.

yes!!!! :D