I'm sorry this person has hurt you. I don't know the size of the hurt, or the importance of the broken promise. But I sometimes find that some people are easily flustered when confronted face to face. When I feel disappointed in one of my friends, I'll usually write them a letter and explain my side of it, and how I feel. It has saved me more friends than one.

I hope that everything works out for the best for you, and I really mean that. I pray it doesn't become a clash of wills. But if I had to say, I would probably say that you are the one who's been slighted. And if that causes you to mistrust the person who made the promise, then you have every right to walk away from them. I just hope it doesn't come to that.