The DVD never shows them handling the turtle. In one scene she is talking to it along the side of the road (with cars zooming past it, no less). In the next scene they show the turtle walking by itself, alone, in the sand. Then the next scene is Nacchi running on the beach. Nowhere do they a) pick the turtle up and carry it anywhere b) show the turtle near any water, just on sand or c) show Nacchi anywhere near the turtle that is walking on the sand.
It's made to look as if they took the turtle to the beach, but for all we know they didn't. Moreover, they never show it dying.
If I say "I'm going to kill you" and then you wind up dead, without any physical evidence how can anyone prove that I did it? Just because I said it doesn't mean I'd do it.