Maybe the nurse has refused to speak to you? maybe she feels you will shout at her and blame her for it and doesnt want to hear it?
whatever the nurses actions, she did not kill your daughter - she did not make her have a cardiac arrest, and maybe angry and upset that she is being questioned about it.
The fact that there was no oxygen mask in the room could have been for many reasons, this nurse may have only just come on duty and can't be blamed for there not being one there...also as she is a junior nurse perhaps its not down to her to ensure there is one in every room...?
And regarding leaving her alone .... what did you want her to do? Stay with your daughter with no mask and thus no oxygen and just watch her suffer ...or go and get a mask...?
also i'm not sure that she would go into a room, wake your daughter just to tell her that... why would she?
but if on a routine check, your daughter asked her how the other person was, or maybe even if she could go and see her... what was she to do...lie? perhaps the nurse thought itd be ok because it cant have been that unexpected given that the person was in hospital and very ill...
i dont blame you being angry and upset - i'd be the same...and i feel for you... but i know you say you dont blame the nurse, but it sounds really like you do, an want to interrogate her ...but try not to see blame when there may not be any and its just a very sad and unfortunate accident.
if they really wont let you meet her, maybe you could ask if you can speak on the phone?
or write her a letter - and ask politely for her account of events and to answer any questions thoroughly... that way she wont feel under attack and may want to help