Questions & Answers about Ona ne želi poderati te traperice.
How would I change this sentence to say she does not want to tear a 'certain pair' of jeans, using the current lesson's topic?
You would replace te (those) with jedne (the feminine plural form of jedan). Because traperice is a plurale tantum (a noun that only exists in the plural form), it requires the plural form of the number one to mean 'a pair of' or 'some'. The sentence would be Ona ne želi poderati jedne traperice.
Why is the perfective verb poderati used here instead of the imperfective derati?
Poderati focuses on the completed result of tearing or ripping the jeans. If you used the imperfective derati, it would mean she does not want to be in the continuous process of tearing them, which sounds a bit unnatural when talking about ripping a piece of clothing.
What case is te traperice in, and why does it look like the dictionary form?
It is in the accusative case because it is the direct object of the action (what she does not want to tear). For feminine plural nouns, the accusative case endings are identical to the nominative case endings, which is why it looks exactly like the dictionary form.
Is the pronoun ona strictly necessary here?
No, it can be dropped entirely. You could just say Ne želi poderati te traperice. Croatian frequently drops subject pronouns because the verb form already indicates who is doing the action. Including ona adds emphasis, meaning 'she' specifically does not want to tear them.