The fact that the person had criminally trespassed, made no due announcement of their presence and was attempting to enter her property absolutely falls within acceptable brandishment in all states of the Union. There is no question that brandishing a firearm in that situation is with lawful excuse.
Now, if she had pulled the trigger, had an unlicensed or illegal firearm in her state, or sought after the fleeing person, then there’s an argument that she commited a crime.