I have that same flowered blanket at home that we use to cover the windows when the sun hits the TV. I'm at work now but I'll take a look at the tags when I get home, if there are any left. Its very old.
And that is very strange. Was not expecting to see something "familiar" in the photos.
For the horse it's hard to say what has happened, the horse might have reared or been scared of something. It might have had a brain aneurysm, a heart attack etc...
But most likely if she had no helmet, she probably hit her head and died from that. A head injury from falling off with no helmet often leads to at least a concussion and major injuries.
If the horse fell on top of her, that alone would probably break her ribs and maybe puncture her lungs. Getting hit with 900lbs in motion is almost surely a lethal blow, especially with no helmet.
So was it determined if she was indeed under the horse or just near it?
No saddle, no reins, no bit and bridle? I can see no saddle but wouldn't it be difficult to ride a horse without atleast a bit and some reins? It sounds to me like someone could have came across this site earlier on and did some looting.
I don't know how possible this is but I have heard of some Native American death rituals that involved the burying of a horse along with the deceased, although it's probably not very likely.
Full list of rule outs as of 30 September 2017: Stephanie Benton 1977 Arizona, Darla Crist 1963 Arizona, Sherry Daughtery 1963 Arizona, Maria Mauricio 1977 Arizona, Adriana Rojas 1978 California, and Tiffany Sessions 1968 Florida.