Is her registration number listed? Appendix horses are still called Quarter Horses and registered with AQHA, but their registration number has an "X" prefix.
It doesn't matter how many generations you breed back to a regular-registered QH-- if a horse has an appendix registered parent, the offspring of regular QH x Appendix always automatically gets registered as Appendix. For their offspring to get Appendix QH papers, Appendx QHs must be bred back to regular registered QHs. Appednix x Appendix and Appendix x TB are not eligible for any type of AQHA papers.
The only way for an Appendix QH to get regular QH papers is to earn a show or race Register of Merit. Once a formerly-Appendix-registered QH earns and is issued a regular QH certificate, its offspring by a regular QH are registered regular QH, and it can also then be bred out to a TB and produce Appendix offspring.
Also, if the registration papers you are looking at are half-Arab, they are not always very detailed about the non-Arabian parent. If the dam had papers with AQHA, most likely they would just call her a Quarter Horse, rather than noting she had Appendix registration with AQHA.