Oh frog. No directly useful advice but just wanted to give my sympathies and
to your DD and to you. That is just so awful.
No direct advice about how to ask for special circumstances, but if you start a separate thread under Secondary school, I reckon there are likely to be people on Mumsnet who will know.
No direct advice about the epilepsy either, because my experience with it is only with a non mainstream child, with a highly abnormal brain, but I do know that there are lots of anti-epileptic drugs out there, and the first one tried may not be the best one in terms of effects and also very importantly, side effects. It might be worth pushing for second opinions on the drug options (I realise that is all time consuming, and it takes time to test these things on any individual, as we all react differently to them, and time is what you don't have). We had terrible side effects from the first drugs tried, and eventually settled on Kepra, which had much fewer. Everybody is different though, and anti epileptic is, I believe, a bit of a hit and miss. Don't assume that whatever your DD is on are the only drugs available, talk to doctors!