ackfoo makes some good points and I would like to add to them as I too have seen the nurses interview.
I also offer my congratulations and respect to the nurse for helping.
I offer this thought, that the nurse's light headedness may have been caused by the following.
She works in an ER at about sea level and does her work in surroundings that do not make her kneel. I imagine she was kneeling to administer to the first two patients. I believe that she was probably dehydrated too. Couple these two together and when she arose from the kneeling position she had momentary Postural Hypotension (head rush from getting up too fast). She was concerned about her two patients and the situation and added things together and diagnosed herself with the same ailment.
I recall a situation on a 737 in the 1990s in which someone fell ill due to LOW oxygen levels. The captain (someone I could not agree with ) indicated that some people should not fly.
I blame the rampant use of recirculated air in the cabin. This situation of recirculated air reduces fuel consumption slightly. On older planes you always got lots of fresh air . Later on you could select recirc to reduce fuel consumption and it was used. Back in the 90's I stopped using RECIRC especially on flights to and from Florida as the folks were older and could use the fresher air.
A plane can be normally pressurized but have reduced oxygen levels. Someone also mentioned that the eyeball air outlets were not working and this can lead to a feeling of insufficient air.
The 8000' limit used in modern planes for cabin altitude was based on studies of healthy 20 year old men during WW2. I STRONGLY SUGGEST that the FAA revisit the question of cabin altitude and ALL normal passengers from young and fit to old and sick...they all buy tickets now a days.