What is the best way to be loving and affectionate with a needy, insecure, miserable mother, living in your home?

My mother has lived her life in a state of self pity. She is incapable of gratitude or appreciation because this would nullify her ability to acquire the pity she desires. She is so wrapped up in her misery, that there is no room for relationships with others. My father was a strong-willed, controlling man that was very family-oriented. He provided for all our needs except affection. Before my mother married him, her Mom was the evil figure in her life. That changed to my Dad once they were married. Once he passed it was my brother because she was sharing her life with him. That situation eventually became so unbearable for everyone involved that she moved in with my youngest sister. She lived there for two years. They took excellent care of her and her finances, but their lack of participation in feeding her self-pity caused her to want to move in with me. She has been here almost 5 months. I would like to have a positive relationship with her and see her last few years be pleasant, but I find her constant complaining about everybody and her distorted view of her life experiences intolerable. She is so miserable that associating with her is frustrating and exhausting. How do I set boundaries for myself, with her, without being consumed with the effort? She has been on antidepressants and it doesn’t make a noticeable difference. I have compassion for her circumstance, but cannot express it because it would be like turning on a faucet that could not be turned off, completely draining me of my emotional resources. I am wondering if it is possible to show her a better side of life, with some creative methods, or do I accept this is her life, by her own choice, and let her sit in her room and feel sorry for herself?