IMHO the easiest explanation is there are still only male Jem'Hadar, but they're capable of siring children with other races, and her mother is a Klingon.
While one could argue that it's weird the Founders allowed the Jem'Hadar, as an engineered race which was grown in a lab, to be fertile, it could be argued that there would be just that much extra intimidation if you feared your daughters could be kidnapped and made to sire half-alien babies.
