My little sister has went through a lot in the past year she was in a pretty toxic relationship that had been going on since high school she is now 24 years old. She got out of the relationship and moved in with our parents she always did better than me in life but then just stopped caring about anything. Now when I say she was in a toxic relationship she and him where toxic to each other they both cheated lied and hurt each other she also became very materialistic. Our parents raised us to have respect and work for everything. As the older sister I see her now living with our parents using them being extremely disrespectful to our parents and just being down right mean and ugly to everyone she also started dating a 19 year old after like a month of living with our parents and now her life is all about him and his family she shoves me away and our parents doesn’t care if she hurts us by the way she speaks to us and honestly just shoved everyone away. Idk what to do and being the older sibling I feel responsible to help my parents who are In their 50’s she makes me so mad to see how she treats everyone. I really don’t know what to do anymore does anyone have advice on how I should handle things should I just leave her alone entirely or should I do something please help.