Maybe all she need was your attention to look at her in every direction so that she will feel your appreciation.
Maybe she loved you with all your flaws but you were too distracted and weren't thorough.
So when her feelings got beaten with all the wasted time and effort. She fell out of love and decided to go on. Without you.
Then she found someone who makes her feel confident and assured.
You saw the same smile when you first laid your eyes on her. You get the cravings of wanting to kiss and hug her. You want to tell her, you love her. That's when you know you still want her.