Attack the nurse all you wish but the "Call 911 only" policy is due to the trial lawyers. If she had done any damage, and broken ribs have now been mentioned several times, she and the facility she works for would probably been sued by some bottom feeding lawyer.
So the facility has instituted the ""Call 911 only" policy and she, as an employee, is obligated to adhere to it.
The problem is that if you do CPR right you will break the patient's ribs on the first couple of thrusts, and if you don't hear the ribs crack then you are not going down far enough to do any good and you are wasting your time.
California does have a Good Samaritan Law, however as long as the nurse or doctors are on the clock they are libel and not protected. However, a lay person walking by the incident could have preform CPR and not be held liable. The nurse refused letting anyone try to save the women.
They are going to be sued anyways and will likely lose. The police are looking to see if any laws were broken for refusing to allow anyone to help. It is an insane world where those who are trained have to watch the untrained preform the work to avoid being sued.