dadcob normally I would say as long as you enjoy spending time with your girl I would stick by her because loving someone is always more important than being in love with them. But what u found in her journal was proof that her heart isn't in the right place with you. It's up to you if you want to be second fiddle to a guy that doesn't deserve her and a girl that doesnt' realize it.
One day the Moon said to me, "If he makes you cry, why dont you leave him?" I looked up at the Moon and said, "Moon would you ever leave your sky?"