Texas law, as written, clearly states that if a reasonable and prudent person has reason to believe that the one running away is an ongoing threat to the community, deadly force can be used. (Granted, the shooting occurred in Georgia...)
Since in this case the woman surely had reason to believe the guy had murdered her mother and kidnapped her, she certainly had reason to believe he was an ongoing threat.
And when the cops publicly say they think it's self-defense, the odds are that it will indeed be called self-defense.
, Art