First off, realize you will compromise the handling somewhat by lowering the bike, no matter how you go about it. If your GF isn't a good enough rider to handle the ZX6R without lowering it then she may not be good enough to ride a modern 600. They are very fast motorcycles that need a steady, skilled hand.
How much lowering do you need? How do you plan to lower the front to match? I made the one set of lowering links I needed out of steel flat bar. It certainly isn't rocket science if you're DIY inclined.
Oh yeah, welcome new guy.
Mark