How to stop 87 old father from moving from skilled nursing to Assisted living against his will and wellbeing?

Talked with Father this morning and they informed him he was moving back to assisted living. We do not know who issued this request. Current DPOA has breached her duties in many ways and this is move needs to be stopped immediately. Need exparte to expose her initiating undue infuence on all the estate documents where she is named as having authority over him and have a judge disqualify them.