I would like to set up a similar thing as you did for your GF, but I don't really know how to do this. Your post is really confusing me, could you elaborate a bit ?

The reason I want to do this is because I have a home PC and a laptop, and I would like to receive my mail on both of them.

First I thought to enable the "leave the mail on the server" option, with the added switch to delete that mail after 24hrs to prevent the flooding of my mailbox.
But your option seems better to me since my provider does allow me to use up to 3 email adresses. Could you please explain this a little bit better to me?

Thanks!