I can't really tell you what the best choice is, because only you and your girlfriend can decide that, but I can tell you that something extremely similar happened to me with a long distance relationship. It was like flipping a switch. I went to visit and it just felt different. He came to visit me a while later, and I knew it was really over.

I still don't really understand it, and even though it was for the best and happened 15 years ago, I still sometimes wonder about what could have been.

LDR can be really romantic. It can allow you to form a fantasy image in your head of what the other person is like, an image that deflates when you spend actual time with the person.