I think your mother talking to herself is just a way for her to vent, relieve herself of the hurt that someone inflicted upon her in the past.
Some people tend to brood over things from the past, sometimes they are more sensitive and hurt for longer periods of time. You sound like someone who likes to be happy and optimistic. You are lucky!
Since you want to help your mom, I suggest that when you see her talking toherself, you start talking to her about something happy and divert her mind elsewhere. Or you could talk to her and help her get it out of her system, so to say, altho there could always be numerous repetitions!
Play relaxing music at home, keep up a happy atmosphere and generally try to keep her happy, I guess.
She is definitely not angry with you.
In a funny way, I understand this because whenever I sense I am getting angry, I sorta talk to myself, I ask myself to calm down. I sometimes imagine what I might have said to the other person to let them know how I feel. B'cos keeping it in my mind just makes it worse.
