I thought about this type of scenario, but I have difficulty believing this was an accidental death. Normal person discovers Alanna in their pool/hot tub/yard, and their normal, non-pervy mind immediately thinks to stage this as an abduction/sexual assault/murder?
Also, if Alanna wandered into someone's yard and was fatally injured or fell into someone's pool and drowned, then the person isn't even at fault. I just can't fathom that they would panic to the extent that they would stage something this grotesque and risk being caught with her dead body in their vehicle, close to their house, in this condition (certainly indicating murder/sexual assault).
ITA. It makes no sense whatsoever to stage an accidental death as sex crime/abduction/murder.
If anything, somebody might attempt to hide the body, not to stage it the way it appears to be a crime by a sex predator.