By itself, her can be an object pronoun. It can also be a determiner (or a possessive adjective).
For that reason, I need to see a sentence or a clause before I know what function the word her has: (1) (object pronoun) I saw her. (2) (determiner) They insulted her brother.
Because the words him (object pronoun) and his are different, I am pretty sure that him is an object pronoun even if I don't see that word in a sentence. However, I am not 100% sure.
Sentences like this one are possible and fairly common: (Who's there at the door?) It is me. Here, me seems to function as a subject pronoun rather than an object pronoun.
It makes some sense to believe that objects are hard to identify before you see, hear, or use them in sentences and clauses.