Is there something I'm not understanding?

My mother told me tonight how disappointed she is in me and my younger sister. My younger sister moved out to spend more time volunteering while holding a steady job. I am still at home with a low paying job that is enough to contribute to the bills in the house and pay my own car insurance, and anything I need personally. I cook and clean when I can. I have not taken the opportunity to leave home because she seems to need me. She has worked extremely hard to take cars of me and me sister. Especially when she was a single mo . Our stepdad of 13 years pays most of the bill. My mom’s hands have numbness from time to time that makes work difficult. She has high anxiety from not being able to work as well as she wishes. She hoped that I would find a better job to support her more since she has worked so hard to take care of me and my sister in the past, and into our adulthood. (Some things were out of our control). Our stepdad is older than my mom. And he has done a lot for my sister and I. She reminds me of this constantly, although she keeps telling him how worthless he is when she is mad at him. She bought a new car that she could not afford. The payments is a large portion of her pay. My stepdad pays her insurance. And her money goes to her car payment, one small house utility bill, and to help her sister take care of my grandmother (her mother) who has cancer. But for as long as I know, my mom has never been content. And we are always a disaapointment. She told me over and over tonight. I am 32, and never felt comfortable being on my own, because I felt I need to be there for her. I contribute rent, pay electric bill, cook, clean. But she says I dont do anything to support the family. And that I live only for myself. And that I am selfish, and says she has never been selfish. Its like she doesnt hear us when we tell her how grateful we are.Says that she is always helping people, and no one else helps her. She keeps on comparing other people’s family life to ours. Any suggestion how I can remedy this situation and make her proud of me.