So sorry to hear this has happened- I understand you can be worried but I think one thing to put ur mind at rest is to realise she is in the hospital and in good care. From such an event taking place there will be procedures to help her out, especially in terms of her exams too. You need to realise, is there anything you can do right now for her? The answer is no, ofc its okay to worry but you also have your future in your hands with your A-Levels. As someone also doing psych tomorrow, all I can encourage is that if you cant properly revise, look over the revision summaries double pages cos atleast something will happen. Don't worry if you cant contact her, nothing is going to happen since she is in hospital. Just try your best to think forward for the best i) smash that psych exam and just try and look over summaries and ii) on a few breaks try and check in and get some info if you can.
The main thing I want to emphasise is that she will be okay especially if she is in the hospital- nothing further will happen and so I hope this eases your mind a bit. I can understand its particularly worrying esp if its someone you love. But rn, stressing and worrying wont help either of you but shes being helped and the best you can do is try and continue as good you can whilst also attempting to function with ur exams.
I assume your family isnt aware, otherwise if they are I would recommend you possibly talk to them and see if you can get in contact. If not, then maybe possibly the school if u have teachers in admin who can point you to get in contact.
Good luck, and please dont worry. She will be ok, and if anything it will help guide her towards improving from now on.