A few hours of low oxygen like that could induce brain damage. It is not something to sleep on.
The oxygen concentration might also continue to drop further, if it has already been dropping.
If they have a pulse oximeter, test it again immediately. If it is not back up to normal, she should go straight to the hospital, or some place that can administer oxygen (fire department, police, etc.).
This is my concern
This woman’s daughter is married and her husband is with her....
...they are, no doubt, monitoring the oxygen level
What do you all want this parent to do?...jump in her car and drive 20 minutes somewhere ......it’s after midnight!
And if her daughter is not home, or sleeping and doesn’t come to the door, what is this parent suppose to do?
Call 911 to the daughter’s house?
In love I am asking this
In goodwill many of you are giving advice and scaring this parent!
What do you expect her to do?
All due respect to all of you, I know you mean well