Nobody staged a murder. They simply dumped a body. The cause of death wasn't even apparent.
Let's pretend for a minute that she was wandering around and saw the pool of the neighbor 3 doors down. She knocks but nobody comes to the door. She takes off her clothes and jumps in the pool in her underwear, and drowns. The neighbor comes home and finds her floating in the pool.
Hypothetically, that neighbor doesn't have homeowners insurance. He FREAKS out -- "I don't even know this kid! I'm not going to risk losing my home and everything I own because the meddling kid used my pool!" So he wraps her in a tarp, binding her legs for easier transport, drives her a mile away and dumps her, then quickly drives home and disposes of her clothes.
I think we need to consider this as a possibility! Seems entirely possible to me!