I have nothing more to give to hateful people

I still get nothing positive from my sister no matter what I do. I spend my days with my little great niece. I make sure she has food to eat. I play with her. I dress her when I take her out for girls night. I wash her and change her for bed. I love my little niece and she loves me.  
Problem - according to my sister, I don't do any of it right! 
But she is not getting up off her behind and doing what I do. She has no problem getting up and leaving to go meet her boyfriend whenever he calls. She drops everything. And still has the nerve to come back and criticize me! At least I am here with my great niece, her grandchild.
I guess running me down makes her feel better about herself.
I am so fed up!!!