Rules Project Entry 3

This summer I decided to catch up on some reading.  Last summer I discovered the Inheritance Cycle by Christopher Paolini, which most people may remember it by the boy, Eragon and his dragon.  I have started to read these books again, so I could refresh my memory before I started to read the new fourth book.  Since I have been adamant on finding grammar topics recently, I have been paying close attention to the words I have been reading and came across a sentence that made me wonder when to use "I" or "me," correctly. 

The above image is from the first book, Eragon in the Inheritance Cycle.  The sentence that I am referring to starts where my finger is pointing and it reads, '"There'll be blood between us when he finds out about Katrina and me," stated Roran.' 

I have always questioned myself when to say "I" or "me" because for some time I always thought it was correct to say "Katrina and I."  I have learned that this is obviously not always the case. 

Commentary:
On this website, http://www.elearnenglishlanguage.com/difficulties/ime.html I learned that it is correct to say "I" when it is part of the subject and when "I" is performing the action.  For example, Sally and I had a great time this weekend, one would use "I" in this sentence because "I" is part of the subject.

One would use "me" when they are talking about the object pronoun, or when it refers to the person that the action of a verb is being done to.  For example in the sentence, Tom told Sally and me to be quiet, Tom is the subject and Sally and me are the object that the verb is being done to.

All in all, Paolini was correct in writing "Katrina and me" because they weren't the subject of the sentence, but the object.