If you seach Sally Wallis pedigree data base (www.pedigrees.zandebasenjis.com), you will see that Delightful Delilah is noted as IND for Fanconi testing, this in the days before the direct test meant that on the linkage test, she would be considered either a Clear or Carrier, but that the test could not determine and she should be considered a Carrier for breeding. You will note that her dam is also IND (Haynie's Quienona). If you then look at the sire Mystic Inferno, he is also noted with the linkage test as IND, so should have been considered a Carrier for breeding. Of course that said, your girl was born before the linkage test was available, so there would have been know way to know.
I know of many of the dogs further back in the pedigree, but the ones in the first couple of generations are all from Puppy Millers or Back Yard Breeders, sorry to say.
Glad to hear that she is on the right medication now, hopefully your vets have talked to Dr. Gonto…...