Since the Emperors who died after her were given the posthumous name of 'emperor' instead of 'in,' she was the last female emperor as well as she was the last emperor who was named 'in' after her death.
ちなみにその後に崩御した光格天皇以降は「院」でなく「天皇」の号を贈られたから、最後の女帝であるとともに死後に「院」と称された最後の天皇でもある。