Take heart from those like Kupari45 who have survived this ordeal.
It is a final act of love that you can offer and you will have a chance to say all those things we generally leave unsaid.
I know from a close friend what an exhausting time this will be for you, but you WILL get through it. So, if you can, take a few hours out for yourself if at all possible, now and then. You need to top up your batteries with short trips into normality and life outside.
I truly hope that your dear daughter has a straightforward, gentle and peaceful death and that you and your loved ones have all the support you need, both emotionally and physically during and after this desperate time.