PMICreations,
That'd work=)
To do this, you'd have to revise the listing once it's active and change the ID tag to that of your friend through eBay's "Revise Item" form.
...or, you could paste the store window html from your friends account into the html editor of your listing before you submit it. She can find her store window html by logging into her Auctiva account and going to Store(tab) -> Store Window -> Store Window HTML. Placing the store window html in the editor will cancel the automatic placement of your store window in the listing.
Good thinking=)
-Mike