How to deal with my father’s girlfriend?

My father who is 87 years old, has Parkinson’s Disease and some degree of cognitive decline has been living with me, my husband and son for about 5 months now. Prior to his move here, he was living with his common law wife of 13 years. He often called me or one of my sisters begging us to come and get him because “she’s killing me”. My husband and I drove out to get him twice and both times he refused to go. I flew out to visit every two months before he came to us. When I visited I sometimes saw behaviours that were concerning to me. My father rarely left the bedroom then and was often quite anxiety ridden (hence the calls to us, I guess). I remember on one particular occasion, my father coming out of his room in a very anxious agitated state. My father’s common law wife told him to go back to bed. He did. I asked her what are we going to do and her response was “I think he’s going to drive himself crazy”. I was concerned. My sisters and I were told by his common law wife that he was being evaluated. She felt he was not doing well mentally. I asked about the results but was told Dad was forgetful but “as expected for someone with his stage of Parkinson’s Disease”.

I should have pushed harder for details, I know. Other things would occur that to me were not appropriate, but were explained away by Dads CL wife. She wouldn’t bring his meds to him for example; she said he needed to do things for himself. I tried to be understanding, after all he does need to do what he can do for himself. Over time, Dad's state of mind was very depressed and anxious every time I visited and he had begun calling my other sisters asking them to come and get him. Eventually my sisters arranged to go and pick him up, at his request. They called me a couple days before to tell me he was coming. To be honest, I didn’t think he would come, but amazingly he did.

Since Dad has lived here he has gone from constant demands to go to the ER or call 911, anxious demands for extra meds (which he didn’t get), from a person that bore no resemblance to my Dad to someone who is much more peaceful. My Dad has been slowly re-emerging. Dad has maintained constant contact with his CL wife since he’s been here and I’ve been providing her with regular updates and pictures. He loves her and I want to respect that, but she also is very upset with my sisters and I for what she sees as conspiring to take my Dad away from her.

She’s coming to visit soon staying for a week and she and my Dad have suggested that I take her visit as an opportunity to go visit my sisters out of town. It seems like a nice offer on the face of it. My Dad though has an appointment during her visit so I asked if his CL wife will take him and attend the appointment with him? He asked me not to leave until after the appointment. I don’t know what to think. I feel like crying constantly the last few days. I’m not sure if it’s reasonable but I feel angry with my Dad too. Any input would be wonderful. Thank you.