see if you can get the GF to meet you at someplace and get a look at settings. Regardless of what they say at the time, they DO have a preference and don't want to be completely surprised (IE not happy). I managed to take the other half a few places with the plan of getting an idea of what she liked. In reality, there was ONE she really wanted above all others. After we left the store I drove around the block and went back in and got that specific one.
It was real funny one day about 3 weeks later when she wanted to go back to the same jeweler to get another look and she got there about 3 mins before I did and looked in the case and that setting was gone. I walked in the store and she said 'they sold my setting'.. so I had to do some fancy footwork to make her believe they could get another one - in hopes she did not find an alternate and I have to eat at least one setting.