How do i break up with my gf without making her feel led on and lied to.

If you read my other posts u may know that i have a gf but ive realised im in love with my friend (M) today confirmed so much for me and i definetly like him. i just need some help on how to break up with my girlfriend who is blindly inlove with me. i genuenly dont want her to feel cheated on because i havent done anything aside from staring at my friend. on one side of this i dont even want to break up with her. i like her too and it breaks me to know how much she loves me. its just hard with long distance.. i could possibly make an excuse that were young and long distance is hard for me? or should i tell her the hard truth that will destroy her AND me? look at my other post for more info.