mm. This happened to me in high school, but it turned out that I finally grew the balls to tell her that I had a crush on her. Of course, she was straight, and only liked me as a friend, but to this day we are still very close, and it has never gotten/risked our friendship.

OP, I would tell your friend if you honestly have feelings for them, cause you never know what the future will bring, and if your friendship is strong enough, it will survive if they don't have feelings for you as well.