Inapplicable Region Code

Hoping someone can help.
We are based in AUS and my fiancee has started a trial account to play with her US friend and she made a NA account.

As she was enjoying it so much, I went and bought her the retail version - NOT knowing there's a EU/NA different.

Now, when we try to input her registration code, she is getting an inapplicable region code error. She obviously want to stay in NA region and want to play with her NA friends - is there ANY WAY to get the code that we purchased from EB gaming to work?