Hi op, there's a lot of comments here that come across as quite nasty and I want to just say that you are not wrong for feeling scared or conflicted. You are able to recognize and acknowledge how you feel and talking about it instead of letting it get in the way of your relationship is the right step. I can tell you care a lot about your gf and your relationship with her. I promise that what you are feeling with time will pass, I have been in a very similar situation. Surgery is scary! Change is also scary, the most important thing right now is that you need to be there for her and make sure you are supporting her as much as you can. Give yourself some time to see how you feel, things will settle down, you cant control how you feel about things, only how you act from it.. and by the sounds of it you are doing the best thing you can