How do you handle the consequences of a self centered complaining parent?

Hi. A few days ago I received a video of someone I do not really know, but it was for me. When I see it I was shocked, I mean, what the hell ??? The video shows a son who feels annoyance because his father is getting old and can no longer stand on his own. The son is shown trying to get rid of his father in many ways by ignoring him, complaining about his constant annoyances and finally taking him to a nursing home despite the pleas and tears of his father. Then the video shows how now that son gets old and has a son who does exactly what he did to his father. And the video finish saying how I look, you'll see or sort of. I do not remember getting so angry. She is a woman, whom I do not know, who does not know me or my mother, who does not know what I have done for my mother, does not know my reality and send me something like that. But why? That woman is a sister of a friend of my mother and my mother has been complaining about me. I know that she loves the "poor me" attitude and being the center of attention, I know that sometimes I'm not as understanding as I could be because I'm still adapting to her memory loss problem but really ... she does not say that she spends all day complaining, that she loves to supervise what I do, that she is always criticizing me and if I complain about something there are problems, I can not say anything ... she tells me that she can not say anything to me, she does not know why I reacted like that, that I must live life calmly and the worst thing is that for some reason I end up feeling guilty and inadequate and I can not tell her what I feel because she would use it against me and telling to others with a poor of me attitude... this is not the first time I have had an unpleasant moment because of their complaints, there are people who told me things about how I should treat my mother, expecting things that I must to do for her, even with a reproachful look. How do you do to handle these situations?