Another possible reason it would make sense for her to be called 'Sagiyama-dono' is that her marriage procession may have departed from Sagiyama-jo Castle where her parents lived even after she continued to live at Inabayama-jo Castle.
また、稲葉山城に引き続き居住していたとしても、両親の住む鷺山城から輿入れの出立をしたとも考えられ、それにちなんで「鷺山殿」と呼ばれたと考えれば辻褄が合う。