Wait. Are you telling me you’re afraid that she’s going to yell at you or cry? (I assume you’re a guy.) Maybe she will – that’s understandable. Since you are posting on this board and people are talking marriage I assume that you are an adult. If you fear violence, this is a different matter.
I think you are being selfish and are afraid of feeling bad. Actually, showing those things would probably be helpful. Women are kind of turned off by selfish and fearful, so it probably will make the break up easier on her.
This is not personal – but my guess is that in a month or two she will be over this. Yes, facing people is uncomfortable, but it is how we behave at difficult times that defines us. Plus, she deserves the chance to find someone with whom she can enjoy a relationship where feelings are mutual.