Generally I would say that being half saddlebred is not a positive point to most hunter people.
If you think there is a market for her being a jumping saddlebred outside the hunter world that her impressive lines will be a benefit to maybe make two ads. One ad for the hunter people, one ad for the saddlebred people.
I agree. Saddlebred bloodlines are not common or looked for in the hunter, or the jumper world... however, that doesn't change the fact that she's a very cute little hunter, but you would probably be better off not emphasizing that she's got superb saddlebred/arabian bloodines in the "hunter people ad". Two ads sounds like a great idea, though... double the chances of selling her :) She's a lovely girl... good luck!!