If you don't have the actual registration certificate or breeders form, I don't think you can register the horse, unless you can get the breeders to register her first.
If you don't have the breeders information, how do you know she is registerable?
With dogs, there are tons of ads selling AKC puppies that say " the puppies are not registered, but can be. "When the buyer does checking, finds out one or both parents are not registered, then the puppies can't be.
I could be wrong, but without the proper paperwork from the breeders, I don't think you can register her with AQHA