Of course people who do the breaking up can feel bad about it. I broke it off with my ex, and I cried all the way through it. What's the saying? "What is easy isn't always right, and what is right isn't always easy." So although she knew that the relationship was missing something - and most likely wanted to call it off before more time passed and it was more painful for you and herself - I'm sure she had a hard time with it.
As for the meeting tomorrow, who knows? What I do know is that often, your first instincts are correct. She felt that something was missing and broke off your relationship; however, because it hurt to do it, she might second guess herself and think it means she should salvage the relationship. But you yourself say that you could see her reasoning, that the relationship was just lacking that je ne sais quoi.
Emotions are high right now, so if her intention is to get back together, hold it off. Spend some time apart, allow the decision to sink in and have some weight. After that, if there's still something pulling you back together, re-examine.
[SIGPIC]http://img409.imageshack.us/img409/2509/glyphmb9.jpg[/SIGPIC]