This is just nature having its way. Undoubtedly, there are countless worse sights around the world that aren't a direct result of nature. It's a good thing our brains are wired to desensitize disturbing images as time goes on; for those who are weak to this sort of thing, yet viewed anyway, I would question your judgement. However, I do admit that these images are highly unsettling. Luckily all of this can be explained by science and biology.
If this was in fact a case of suicide, and not foul play, accidental, or drug-related, (or a hoax), then shame on anyone who knew this girl including family members and neighbors. The body must have been there for an absurd amount of time - and, this must mean she lived in a house/apartment in the middle of nowhere. If honestly nobody noticed the total dormancy of her place for many, many weeks, then I am just completely baffled. Remember to pay attention to those around you. Be a friend where needed, and never pass up an opportunity to brighten someone else's day. If nothing else, check up on someone if you notice they have been absent for more than a few days without warning.
Also, the "natural selection" argument is totally insensitive and unnecessary. Respect the dead.