Did the edited version have the same file name as the orignal? That's probably why it indicated that it was already in the library. But you don't need to save the editied version outside of the library and import. Did you have Elements setup to work from within iPhoto.
Here's how to use PS Elements from inside iPhoto:
Using Photoshop (or Photoshop Elements) as Your Editor of Choice in iPhoto.
1 - select Photoshop as your editor of choice in iPhoto's General Preference Section's under the "Edit photo:" menu.
2 - double click on the thumbnail in iPhoto to open it in Photoshop. When you're finished editing click on the Save button. If you immediately get the JPEG Options window make your selection (Baseline standard seems to be the most compatible jpeg format) and click on the OK button. Your done. 3 - however, if you get the navigation window
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that indicates that PS wants to save it as a PS formatted file. You'll need to either select JPEG from the menu and save (top image) or click on the desktop in the Navigation window (bottom image) and save it to the desktop for importing as a new photo.
This method will let iPhoto know that the photo has been editied and will update the thumbnail file to reflect the edit..
NOTE: With Photoshop Elements 9 the Saving File preferences should be configured as shown:
I also suggest the Maximize PSD File Compatabilty be set to Always. In PSE’s General preference pane set the Color Picker to Apple as shown:
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NOTE: If you want to use both iPhoto's editing mode and PS without having to go back and forth to the Preference pane, once you've selected PS as your editor of choice, reset the Preferences back to "Open in main window". That will let you either edit in iPhoto (double click on the thumbnail) or in PS (Control-click on the thumbnail and seledt "Edit in external editor" in the Contextual menu). This way you get the best of both worlds.
OT