Because in a parthogenesis event, one set of the mom’s chromosome’s are duplicated. In this case, the mom was homozygous desert ghost/has two desert ghost alleles, which means that no matter which chromosome was duplicated in the partho event, it’s going to produce a homozygous desert ghost offspring. Had the mom been het, a partho event could produce either normals or desert ghost (if we ignore the butter for now) depending on which chromosome was duplicated.
Unfortunately partho animals are known for shortened lifespans and being reproductively challenged (refer to this thread Parthenogenesis and null allele), so I would be hesitant to get too excited about getting a clutch from her if she is a partho baby