She was executed. And her father said exactly that. This time the author is not taking liberties.
Execution occurs when a person stands before a judge and jury, is found guilty of a crime, sentenced to death, and then executed.
When anyone else singles out a person and kills him/her, it is murder. It makes no difference what the father says, it was murder.
Perhaps what they meant to say was "gang execution style murder", you know, the NAZI technique.