In the event that the dinner is still to take place, it may be helpful to just be yourself. Whatever had transpired in the past is finished. At some point the two of you could discuss what led to the breakup whether or not you're to get back together. Each one may need some sense of closure about the past hurt in order to move forward.
As far as what to do to find out if she feels the same way, you would know because of her behavior. Someone who is disinterested would not be going out again or setting up meetings in cozy places. You'd need to know if she's entertaining the idea of seeing someone else/where she stands in the dating field at this time.
Taking things at her pace can show her that you do care and that you respect her comfort level. You can invite her to another dinner or movies (to places that the two of you enjoyed while you were together) When you part from the dinner or meeting, you could kiss your hand or give her a hug (something that does not seem to be coming on too strong yet showing affection).
Depending on the feel you get from her, you could always ask if she would like to give the relationship another try (it would depend on how much she got hurt in the past and how far along she's in dealing with it).
She's not dating or seeing anybody else - I know from our mutual friends. The thing she said to me over and over is that she is thinking about me and us getting back together but she doesn't trust that I would act differently toward her in anyway that I did and that she would be hurt all over again. Yes, the dinner is still taking place, tonight, and I'm very much looking forward to it.