It sounds to me like your father just mimics what he has heard from his lady friend. I think it is an insecurity thing but I don't know what makes these men tick. They have NO mind of their own. I hope Dr. Phil does a show on this subject. Stupid or ill ? Which is it ? It is not normal behavior. I find my husband does this too. I didn't notice this about my own husband until we were married for more than 20 years. Now, when he repeats me or agrees with me on everything I say...I get angry. I feel like I am living with myself. One of my sons is like this too. He repeats everything his wife says. If she says the sky is red, then it must be. My other sons don't have this problem, so it can't be ALL men. My brother is also like this with his wife. Now that I am older my antenna's are up.
I am so sorry for your situation. You already lost a mom and your dad is preoccupied in his own mind?
Ask Dr. Phil if he could help you.