<human>: Condense the text into a few key points

This girl seems like a nearly perfect person for me, but I have this gut feeling that I don't want to be with her forever. We both are engineers and are on the same level intellectually. We both love sports and enjoy lifting and running. We both have a witty sense of humor, and had a lot of the same friends in college. I keep on having a gut feeling, though, that she isn't the one for me. I don't feel the spark anymore when I think of her, and I kind of see her as an awesome best friend that I'm not physically attracted to anymore. The main issue for me is this decrease in physical attraction.

We are working on opposite sides of the U.S. for the summer and will be doing grad school just as far apart. Due to our different engineering disciplines, it seems very unlikely we will get the jobs we both want after college ends in a year. 

Should I listen to my gut feeling and break up with her, or is my decreasing physical attraction to her expected after 2 years of dating? If I were to break up with her, how can I respectfully do it across the country and not in person?
<bot>: Extremely compatible with girl of 2 years, except I've lost a lot of physical attraction for her. Having doubts due to gut feeling and long distance.