What a difficult situation.  We are sorry to hear about how this has all blown up.  Unfortunately, there is not much else to do about this situation at this time.  If you continue to press the issue with the school, you will likely only be met with fiercer resistance, which could make things worse for you and your daughter.  You could go up the ladder to administration, but since it sounds like many of your concerns are based in rumors, this will also probably get you nowhere and may further ruffle feathers.  It's a tough situation to be in, however, provides a great opportunity to teach your daughter about some great and valuable life lessons.

#1-We don't always get what we want, even if we work really really hard.  AND THAT IS OKAY!  Albert Einstein was a terrible student, but went onto be one of the greatest minds in history.  Michael Jordan missed over half of the shots he took in his NBA career, he had a 49% career field goal percentage.  Its not how many times we fall down, but that we stand up that defines character.

#2-You are going to have to deal with people and situations in life that are messy and unsavory.  It sounds you and your daughter have dealt with some people who have not treated either of you with respect or kindness through this situation.  Role modeling and talking about how to most appropriately deal with people who do not treat you kindly is extremely powerful.  This is not the first time somebody will treat either of you badly and it won't be the last.  So how do you deal with people like this in a respectful and polite way without reducing to their bullying tactics?  It is a great conversation to have and gives an opportunity to talk about healthy coping skills, respectful behavior, and self control.  

#3-We can only control ourselves.  In situations like this it is easy to say so and so should have done this and he or she should have said this, but often these sort of wishes and arguments only frustrate us and make us feel powerless.  Don't focus on what other should or could have done.  Try to focus on what you did or can do.  Saying things like, "I am proud that I worked my hardest on that cheerleading try-out and I know I did my best" focuses on you while "They should have put me on the team and they are just trying to get back by keeping me off" are very different messages to send yourself.  Help your child to recognize the positives and silver lining within the parameters of things they can control.  

I hope that as your daughter continues her schooling she continues to try out for cheerleading.  I wouldn't want this bad experience to spoil it for her future.