This is so easy to say about people of all variaties, but we are all different, we all have different fears et,c it is all about understanding them.
You/we do not and never will understand those younger than ourselves, i am sorry to say.
But that does not mean we cannot find a connection of some sort.
Despite what you've said so far, I can agree with that.
A lot of people say they understand children, or that they've "been there", and I don't doubt that, but everyone is different. You may understand a lot of children, and you may have been in the same situation, but everyone thinks differently, and there is no real way to know how she is feeling without her opening up to you. Yes, there are guidelines. Yes, there are connections, and general trends. But there are no set rules, and this is why you need to try every (reasonable) piece of advice given.
For some people, moving school might have worked, for others, they may simply get over it. Some might have needed a psychiatrist, some might have done nothing about it. But what worked for them, may not work for your daughter. However, that does NOT mean you shouldn't try them. In my opinion, I think you should let her sleep now, if you haven't already, take a week off work, and start following advice in this thread day by day. I know you want to get her back to school as quickly as possible, but this isn't something you can rush. Go through the advice properly and thoroughly, and if it doesn't work, try something else. Just don't dismiss it before giving it a good go.