How to decide?

I have been working with a ring designer to create the perfect ring for my girlfriend. She created a lovely ring based on what we had talked about, the limited instructions given by my SO, and inspiration images. But I find it very difficult to pull the trigger. I want the peace of mind to know she will love it, since she will be wearing it the rest of her life, but I want to maintain the surprise of the ring I have created. Can anyone provide feedback, or give me a kick in the pants one way or the other on how to make this decision?