How do I sync iTunes music to two different iPhones on two different user accounts?

Thanks for the response. We are using two different user accounts on one computer and both have our own Apple ID. I just want her music files to show up in my iTunes. I tried adding the media folder where her's are stored, but it duplicated everything (even starting from scratch with nothing in my iTunes). I also do not know if by doing it this way, any music added by her in the future will show up on my end automatically, and if it does not, will it duplicate the music again when adding the folder to get the new stuff.

I followed the following articles: http://support.apple.com/kb/HT1495 and http://support.apple.com/kb/HT1203

Here are the questions I have regarding the second article which is not clear to me:

1. When dragging the media file to a public location, the article says not to move the iTunes folder. Is it Ok that the media file is moved out of the iTunes folder when dragging it to the public location? Is this what I am trying to accomplish?
2. There is a note about how iTunes for Windows does not, by default, copy items added to the library to the media folder. Am I supposed to check the box to allow this? Do I do the same for all users?
3. When I change the music folder location, am I changing it to the new public location? Do I do this for all users on the computer that wants to use the same music files?
4. I tried changing the file location to the public folder, but received a message asking something to the effect of renaming files to keep the library organized. Do I want this or not?
5. There is another note at the end that says if all users are storing their music in the same public location, then duplicates may appear in the library. Isn't what this procedure is basically doing? Can someone clarify this?
6. After following this article to the best of my ability, my iTunes ended up with duplicates of everything, even starting off with nothing there to begin with.