The law in some states permits a citizen to employ force to effect a citizen's arrest without having been requested by an officer to assist. The requirements vary among jurisdictions, but no one in his right mind would want to expose himself the civil liability.
Over my many years of being on this earth I have made two of them. Something’s an officer can make an arrest from witness statements and sometimes by the citizen doing it, it makes a stronger case. in this case there was a sexual act, disturbing of the peace, endangerment of a child so it would have been a solid case and if she was to use deadly force. I could only assume because of the child it would have been justified in any state