How do I balance being good friends with a girl may have feelings for and being loyal to my gf?

My girlfriend and I are in a long distance relationship. We have been going for two years and there is some stress from the long distance but I am generally happy. At school there is another girl who I am becoming good friends with. I am not madly in love or anything but I know if I was single I would be interested in. I don't want our relationship to develop in a way where I may get tempted. How do I balance this?|||You have to act crazy rather than sweety.