She gave her heart away too many times and was given nothing in return.  The only thing left for her was hopelessness and the promise that no one would ever love her in the way she wanted to be loved.  She eventually gave up on the idea and closed herself away.  She had no desire to let her heart be broken again.  Yet when he comes along, she can't help but let herself confide in him.  He understands the pain of a broken heart.