Is my mother actually paranoid or just acting? Why would a person act paranoid?

I live with my mother, who is 81, in good health but very needy and unable to cope with living on her own.

Dad died five years ago and I moved back home because she said she could not manage without me.

Since the Covid Lockdown, she has been talking about me as if I am not there - but right in front of me. Sometimes, she talks to herself, other times on the phone to my sister. She complains about me, calling me "a b***h" etc.

I try to ignore it. When she resumes conversation with me, she acts as if she hasn't said anything at all about me.

Yesterday, she was grumbling about me to herself, in her room with the door open. I could hear her from the kitchen, and was just about to go into another room (so as not to listen) when I heard her crying. I went into her room, asked her if she was OK, and she suddenly stopped crying, smiled and said, in a cheerful voice, that there was nothing wrong, and changed the subject.

Today, we were in the middle of a conversation (about the neighbour's dog attacking a cat in our garden, what to do to stop the dog coming into our garden, etc) when she muttered under her breath "That b***h wants me to sell the house". I looked at her and said "I was talking about getting the fence fixed..." She suddenly accused me of "interfering, hanging around, listening to me when I'm in my room!" I denied it, adding "I was just worried when I heard you crying".

She ranted for a few minutes, and I just got out of the kitchen, and sat in my room until I heard the TV downstairs and the smell of fried food.

I know she is grieving over the loss of my father. I cry too. When he died, she used to berate me for crying. I was actually afraid to cry in front of her, but couldn't stop once the tears started. I never minded her crying in front of me. We both attended a support group and they let me cry - but even in the group sessions, she got irritable if I cried, as if I was embarrassing her in front of other people.

She has grandchildren, and chats with them every day, but when I suggest she might like to live near them after the Lockdown, she gets angry at me and says she doesn't want to live near them because they'd be "dropping in every day" and adding "I don't want teenagers in my house". It was actually her idea to move to their town, and she got me to waste weeks looking for small houses and apartments in the area, but she suddenly went "off" the idea after I said I would not live with her in a small flat, but could live near her (I admit I saw it as an opportunity to reclaim my freedom). Now she believes it was my idea to move - and accuses me of trying to get her out of her house. I don't know what she wants (apart from the impossible: Dad to still be alive, the family to be united, and me as her personal slave and emotional scapegoat).

What I need to know is: Is she paranoid or is it all an act? If it is an act, why is she acting paranoid? Also, why is she so hostile towards me? And why does she get so upset if I mention that I could move out to give her some space? Does anyone else have this problem with an elderly parent? What do you recommend I do? Sorry for all the questions...