Excessive thoughts about being deprived.

My mother is a housewife and doesn't have major health issues. Her mental health seems problematic since she keeps talking about past family issues excessively for hours and days and most of the time doesn't realise she has said it enough. She has this habit for years and keeps nagging all the time. She has a feeling that she is deprived of luxury and money while she has no financial crisis in a middle class environment. Her nagging talks turns into dramatic screaming and hyper action if someone tries to pacifying saying whatever she has now is good enough. I being the daughter have grown hearing her unnecessary screaming  and that has impacted my studies, self esteem, morale. She is now widowed however there is no change in her behaviour... Is there any medical help to calm her down and be at peace with whatever we have?