Another vote for dunskin...but, jeez louise - that hock! Did the breeder even treat it when it happened...or since? (didn't look like it in the earlier pics). I would think long and hard before purchasing her. The hock is not an area you want to just let go...and all that swelling makes me think there's infection going on and/or scar tissue developing. This can interfere with future soundness and performance. A shame, because she's a very pretty girl.
I vote bay dun. Unless her sire happens to be a smoky grulla, which wouldn't be known without testing (or if he has sired a dilute foal out of a nondilute mare), she couldn't be a dunskin. Bay duns are often mistaken for buckskins (or vice versa. I had several campers over this summer call Abby a dun).