Well, I'll play the devil's advocate I guess. While it certainly sounds like this girl was NO match for the horse, I had a similar experience, except I was the one in the buyer's shoes!
When I went out and looked to buy my Foxtrotter last fall, they had her pre-saddled and everything and had this really weird metal bosal on her head. I mean it looked just like a rawhide bosal, but it was metal.
I couldn't steer her for the life of me. It didn't matter if I used one hand or two. I just couldn't get the hang of how to work that bosal thing and the horse wasn't going where I wanted. She was also used as a rental horse and had lead sides, so using leg aids didn't seem to do a thing.
So the older guy that runs the rental program proceeds to give me a lesson. I felt like a total beginner! Now I am not a world class rider or anything, but I have been riding for about 15 years and manage to ride the trails, mostly by myself, almost every day the weather is good for 15 years without getting myself into much trouble. Anyway, the younger guy who was there, who was actually the horse trainer, told me the mare would neck rein and I didn't have to listen to the older guy so much because he didn't know the horse as well as he did. When I asked what bit to ride her in, he said a halter!
So I bought the horse because it was one of those "buy her now or she goes to the auction next week" kind of things, and my long time horse friend told me she would buy the horse from me if she didn't work out. So we went and got a trailer and I bought myself a Foxtrotter.
So as horrible as that all sounds, (and did I mention she had a foal at her side that they were selling separately?) I ended up with a REALLY nice trail horse who neck reins and has a really soft mouth and is really sweet and kind. We are working on leg aids and I even have her side-passing. She neck reins and direct reins (depending on what we are doing) great!
So I guess the point of the story is, I went out to buy a horse, I couldn't steer her and I'm sure they thought I was really ignorant, but it all worked out great. I still don't know what the deal was with the metal bosal. I think maybe the trainer used that on all the horses he was working. But she takes a mild bit great and I've had not a drop of trouble riding or steering her since I got her home.