Wow, so sorry that your friend kinda "stabbed" you. Yeah, those disappointed feelings kinda piled up and made you can't concentrate well, then in the end you find yourself guilty for over thinking it. Maybe you felt a quite similar feelings as me..
But have a strong hard haha. They said let bygone be bygone right? From the hard feelings we get from these events, there are also lessons to take, and someday those lessons are gonna take part in our life. Letting go is also an important thing to do, and I will learn to let go of hard feelings from this
its not really her fault since i didnt know that she had it until like, a day before the event.. but yeah i felt a bit disappointed, probably not as much as u did for ur case at the time.. but no doubt i've felt, whole-heartedly what u've felt. just try to be a sponge and soak it in, then when u can, just squeeze it out..
.. or u can just cry ur heart out, thats always a faster way and less 'painful' one