the rights aren't hers to sell in the first place.
Exactly what I was about to say. Christy is the distributor, and manufacturer, but she does not own the rights to the product.
It's the same difference between developers and distributors in film or the game industry, trying to buy the right off Christy is akin to trying to buy the intellectual rights for a book from a print house and not the author.
At best, Christy could sell off her part manufacturing rights, but that still doesn't give her the right to sell product's intellectual rights.
Though this is assuming the kingdom has any intellectual protections at all. Patents and copyright were only made after a influx of intellectual theft cases where there were no laws to protect the victims.