As everyone else, I would get a vet out. I don't know about the area you live at, but at the sale barns around here, you wanna be extra careful in what you buy. They say the horses are 'vet checked' and tested for drugs, I don't know how they do that. But I have seen some horrible things there.
Just the fact alone that the horse came from a sale barn, you need to get her checked. There are a lot of diseases and problem horses that go to these things and NO ONE will tell you ANYTHING bad about the animal. Heck, one time I went, a gelding was alive and standing the first time I passed him, an hour later, he was dead.
Some guy rode a horse with a bloody poll into the ring. Blood was running down this mare's face and they were selling her has a broke, reliable horse, even though she banged her head by rearing in a trailer. Horses have gotten fat that quickly. You'd be surprised, so there is reall know telling. But for her sake, and other horses, I would check her for diesease or illness she could have caught at the auction.
Lettin' the cat outta the bag is a whole lot easier than puttin' it back. -- Unkown