You can't use deadly force to protect property . Only people .
You are correct.
I have a Juris Doctorate, so let me explain to the rest of you how the law works. In all jurisdictions the use of deadly force is allowed only when – at the time such force is used – a person reasonably believes it is necessary to prevent death or serious bodily injury to himself (or an innocent third party). When a suspect is running away he obviously does not pose a such a threat. Even the police have no right to use deadly force to prevent the escape of most suspects including those who have broken into automobiles. The police can use deadly force only to prevent the escape of a dangerous felon. The law defines a dangerous felon as someone who has inflicted or threatened to inflict death or serious bodily injury. Breaking into a person's automobile does not make a suspect a dangerous felon.
The leading case regarding when the police may use deadly force to prevent the escape of a suspect is Tennessee v. Garner. In this case the United States Supreme Court (SCOTUS) reviewed a Tennessee law which allowed the police to use deadly force to prevent the escape of non-dangerous suspects The particular case involved a man who was suspected of burglarizing a home. The following are the relevant portions of the SCOTUS decision:
“The Tennessee statute is unconstitutional insofar as it authorizes the use of deadly force against, as in this case, an apparently unarmed, nondangerous fleeing suspect; such force may not be used unless necessary to prevent the escape and the officer has probable cause to believe that the suspect poses a significant threat of death or serious physical injury to the officer or others.”
“While burglary is a serious crime, the officer in this case could not reasonably have believed that the suspect - young, slight, and unarmed - posed any threat. Nor does the fact that an unarmed suspect has broken into a dwelling at night automatically mean he is dangerous.”.
“The use of deadly force to prevent the escape of all felony suspects, whatever the circumstances, is constitutionally unreasonable. It is not better that all felony suspects die than that they escape. Where the suspect poses no immediate threat to the officer and no threat to others, the harm resulting from failing to apprehend him does not justify the use of deadly force to do so. It is no doubt unfortunate when a suspect who is in sight escapes, but the fact that the police arrive a little late or are a little slower afoot does not always justify killing the suspect. A police officer may not seize an unarmed, nondangerous suspect by shooting him dead. The Tennessee statute is unconstitutional insofar as it authorizes the use of deadly force against such fleeing suspects.”
FindLaw's United States Supreme Court case and opinions.
Conclusion: the lady broke the law. Her only hope is for a sympathetic jury. This is not debatable.