I heard this about 50 - 60 years ago...try blowing a short, sharp, small breath in her ear, with your lips tight over your teeth...not to get air INTO her ear but to engage her hearing reflexes, I believe.
...Just enough to startle her awake.
However, it may never happen again, so you won't need the hint.
Maybe not worry what it was...only think of what she needs...as you naturally do with everyone.