Care to much or need a life?

I am single no children, but love my nieces and nephews with all my heart. I have always been assured by my sister that I have the right to tell her kids right from wrong. Yet she herself does not know right from wrong and when I state my concerns she agrees but then when I'm not around tells her kids not to worry about it. If I state my concerns about that she treats me like I'm acting like an idiot and worrying too much. I don't understand how any worries about safety of a child can be too much. Especially sincev we just lost a child last year. I am distraught and feel I am being pushed away. I wonder should I just move on and worry about my own life now? Everything I do or say anymore is taken out of context, blown off as stupidity by her as well as her kids. Who are teens.