Bali will be a good place since your girlfriend is not diving. It doesnt matter where you choose to start because Bali is a big place. If you are staying for a while, you probably move around anyway. Bali also offers different variety of diving. Plus, there are more flights in Bali for your visa run and you can travel easily to Komodo, Gili, Lombok from Bali. Sanur will be a good place to start.