Certainly. Here is a girl who was on an island. She disappeared while on said island.
They seemed to have located the people responsible for her disappearance, and they have located things that suggest she met with foul play.
And, again, she was on an island. Exactly how many places can you hide someone on an island? Certainly not in a pond.
Is that simple enough for you?
I don't see how you can be so sure they've located "located the people responsible for her disappearance." Up to this point, there seems to be little evidence of that.
And I'm not aware of any evidence whatsoever (again, up to this point), that shows "she met with foul play."
If you know of such evidence, I hope you'll post it.
And, again, she was on an island. Exactly how many places can you hide someone on an island? Certainly not in a pond.
I have no idea what to think of this "pond" thing. It doesn't seem likely to me she's there, either. I suppose we'll know soon if the "pond" thing turns out to yield real evidence, or is just another wild goose chase.
However, your question "Exactly how many places can you hide someone on an island?" ignores the possibility she was "shipped" to another island, or to the South American continent.