Yes, PG, I know which lake you are talking about and there are people that live on the lake full time in houseboats. I can't believe someone wouldn't have noticed bullets being shot and called the police.
I think your theories are valid but the fact that you believed her story at first makes me think that she truly believed it which is why it was so convincing to you. That's why I think this all may be meth induced psychosis rather than a made up story.
Of course, our difficult child's are very, very good at making up stories.
Either way, this would break a mother's heart so I understand how you must be feeling right now.
~Kathy