iPod & iTunes Question

I have questions about iTunes & iPod; but before I ask them, my sister and I copied each other's songs off of our iPods. So, what my questions are is that since my sister's songs aren't stored on my computer, do I have to create new folders with the artist's name and album name or will I not have to do it because my iTunes will do it for me? Also, will something bad happen if I open my iTunes library, even though my sister's songs aren't stored in iTunes and on my computer? Furthermore, I'm sorry if I'm wasting everybody's time by asking these things, but I was never in this situation, before.