Why don't they tell me....it's pissin me the hell off!?!?!?!?

Don't ume that your sister did ANYTHING, maybe something was done TO her and to make sure the proper information gets to the proper people involved it is sometimes necessary to keep parts of the information from others until the situation is resolved. Sounds like your sister could use some support not some sibling rumbling around about being dissed by not being included in the decision making. In time you will know what everything is about. Patience is a virtue, remember this.