Subject/Verb Agreement

Question

Given that I, me, she, and her are all singular pronouns, why are both of the following sentences correct?

I disagree with her.

She disagrees with me.

Answer 1

In your first sentence, you (the I in the sentence) have found fault with her logic.

In the second sentence, she has found fault with yours.

So, forgetting about whose logic is better, can you see that when we use first person (I) as the main subject, it remains "I." When it is the object, it is only "me." Most of the Latin languages are like this as well. In French, it is Je and Moi. So... the other pronouns are like this as well.

Answer 2

As you correctly stated, they are all personal pronouns. A sentence expresses a complete thought. The correct use of words in a sentence will guide you to express a complete thought correctly. A sentence will be correct when you apply the correct order of words and the rules of grammar to your writing accordingly. You already have part of the answer in the title of your question. Sorry, no direct answer but this will definitely guide you to find the answer with what you already know.