Is it possible that one of the boys called 911 and when they said sister, they were referring to Isabel being the "sister"?
I've had numerous dealings with TPD and calling 911. Sometimes what you tell the dispatcher gets skewed until you talk to an actual officer. The whole picture of the story usually comes together when you talk to them. Just my experience.
That is a really good thought. Boys their age could very easily be mistaken for being female on the phone.
Without hearing the caller I think a big deal is being made over something that might be nothing.
All of this is MOO