This is from the AZ State Bar website and is a portion of the self defense/deadly force jury instructions. I think her claim fails on 2 prongs - apparent danger ends (she has an escape route) and gun was excessive force because she was being "attacked" by a naked/wet/unarmed person.
The use or threat of [physical force] [deadly physical force] is justified only while the apparent danger continues, and it ends when the apparent danger ends. The force used may not be greater than reasonably necessary to defend against the apparent danger.
The use of [physical force] [deadly physical force] is justified if a reasonable person in the situation would have reasonably believed that immediate physical danger appeared to be present. Actual danger is not necessary to justify the use of physical force or deadly physical force.