What I don't understand is, if she doesn't want to sell him with papers and be shown, then why bother bragging what his bloodlines are? Just don't mention it and let the horse be sold as is, as a grade and destroy the papers. My guts say don't buy.
Papers for a gelding are just a birth certificate and ownership title, but she won't need them and selling the horse means giving up control. She should consider leasing if she's not really wanting to give that up. Or she's really wanting the larger sum, but regardless, it's shady.
You don't buy a car from someone and they brag that it's a ferrari, but will cost you more to have the hood ornament and title because they don't want you to drive it certain way, though it's made to be driven.