I can't seem to post videos to here but John Correia did a very good frame-by-frame analysis of the shooting. He thinks that the malfunction was caused by a poor grip on her part. He also shows that she did not clear the malfunction on her gun. When he slowed the video down you can actually see her attacker take a swing and he slaps the gun and jars the slide stop loose. About a second later she does a Tap Rack Bang and you can
clearly see that the gun is already in battery before she starts.
Michigan Deputy Defends Against Encroaching Attacker - YouTube