Mom is struggling with memory issues and every time I try to assist her she feels like I'm taking away her independence. How can I cope?

my 94 year old mother in law is struggeling with memroy issues. She is storngly independent- has 2 sons- one with mental health + a sister. She has good and bad days. She lives alone- my husband and I live in an in law apart next to her. She also has $ - she is struggling with memory, health and ADL's. Any suggestions I make to assist in any of these areas she feels I am taking away her independence. Her 2 sons and her sister are willing to just let it take its own course. She is lonely and depressed when I go into to be with her- again any suggestions appear to make things worse. Her 3 grandchilren from her other son are financilly taking advantage of her. Almost to the point that she is willng to put her own financialy future in jeoprdy becasue she can not remeber what she is doing. Due to the fact that I am th in-law I have been put to the side except for the fact that I do the bulk of errands, listening, picking up the things that are dropping - I have spoken both to my husband and her sister, who does not live by who feel that there is nothing that can be done about the sitiuation. I get overwhlemed with my own feelings of inadequies, anger and frustration at the entire situation. Does anyone have suggestions