That's all Florida's Stand Your Ground law says. She doesn't have to try to outrun the bad guy or overpower him hand to hand.
It's just common, Hollywood movie sense:
1. Are you an innocent person being attacked?
2. Do you think that turning your back and trying to escape you will be killed?
3. Then you can use whatever force to save your life.
Here's the actual complete wording of Florida's stand your ground law:
"A person who is not engaged in an unlawful activity
and who is attacked
in any other place where he or she has a right to be
has no duty to retreat
and has the right to stand his or her ground
and meet force with force, including deadly force
IF he or she reasonably believes it is necessary
to do so to prevent death or great bodily harm
to himself or herself
or another or to prevent the commission
of a forcible felony."