tess1pink. I really sympathise. Only you and she can know if she is really mature enough to cope. If she isn't, an extra year doing amdram and college might be the answer. Does she suffer from anxiety, generally, or is this a first? As others have said, extreme anxiety before she has even gone away could be a cause for concern.
My dd went last year and found the first few weeks tough. I texted every day and talked to her on the phone and Skype when she was homesick and miserable. It can take a while. There is this myth that everyone loves it immediately. Not necessarily true. If you are lucky with your flatmates and the people you meet at Freshers, fine. Otherwise you have to persist. I would advise joining societies and trying to meet a mix of people, especially if you are on a course with few lectures. And always remember that people find it hard to admit they are struggling. Some people drink a lot and seem to be having a marvellous time, when they are really feeling homesick and a bit overwhelmed inside.
We went to see our dd halfway through the first term and we fixed it all up before she went so that she would have something to look forward to. I think coming home too early can be a mistake, because it is so much harder to go back and settle down. My dd really started to enjoy it during the second term.
But I also agree with Emily - if you really hate it long term there are other options, like transferring nearer home or doing something else. Higher education isn't right for everyone. You have to give it a good try, though. And as someone else said, being at home might not be a picnic if all your friends have gone to uni. It won't be the same anyway.
There are a lot of sides to all this and everyone is different. What is right for one person might not be for another. The best of luck to you both.