I was mainly going on the fact that there was a very similar horse run through the Camelot sale a while back with just that color. They called it a Rocky, mainly because they can wiggle a couple dollars more for the horse and they are easier to sell. Later Camelot ponied up and changed the horse to a Tennessee Walker. Truth is you can call them anything you want, without papers they are a grade and valued less unless you register them with the Kentucky Mountain Saddle (if they are still allowing appendix mares), but in general they still aren't aren't valued much above a grade since you have no lineage. The appendix registration with KMSHA is also very pricey to get done.
Champagne is in many of the Tennessee Walkers now and still not so common in the Rocky and Kentucky mountains. In fact it is still pretty rare, so the odds are against someone dumping a champagne mare unless she was a problem. They would keep her for breeding if nothing else.
My feeling is still that the horse is a Tennessee Walker (which are very common breed in the Kentucky Mountain registry) and without papers it doesn't really matter.
Regardless of breed, she is a very pretty color and I like the rest would love to see some larger better pictures.