I know, when such things happen with people whom you consider very close, it does upset you. I think you can take your time to feel better. I can visibly feel through your question that you are hurt right now. So, when we are hurt, there is no need to walk away from the emotions you are feeling. Take your time, and if you do not feel like talking to your SIL for sometime, do not. Probably when you will not talk to her as often as you do, she would realise that she should not have behaved the way she did. If you were close then instead of diplomatically making you cancel your programme, she could have straightaway told you to make your trip later sighting the reason that if you will come now during her kid's exam, she fears that he won't study and will not do good.
Anyway, let us forget what has gone by. I suggest, do not over think now. Whenever you are ready to hold a normal heart to heart conversation with her, have it, and then can express that you did not like her behaviour. And if by then, your heart has healed on its own, no need to bring the topic back. People whom we love, sometimes, do not meet our expectations, and it happens with each and everyone.
Read more