I’m so stressed out...

I have been ignoring my 10 yr old niece because she has been rude/been bullying me for days. I struggle with depression,social anxiety and general anxiety. Yesterday I got out of my room to take a picture in the living room for an ID I need. She then says “you should go do that in your room” every time I go to the kitchen to get something to eat she says everything is hers and I can’t eat it, today my grandmother decided to help me make something and she was like “are you making that for me” “why are you making that for her she already ate yesterday “ she wants me to give her the WiFi password but I changed it Bc her behavior is getting worse and my grandmother who has custody isn’t disciplining her. So then she says” I’ll punch you little girl”. My mom wanted to talk to me bc she didn’t speak to me all day and she came and said grandma let’s go over here I need to talk to you about something. My aunt came over and was talking to me and she came over to try to take away her attention from me. When my bf comes over she’s like go hang out with your little boyfriend you never spend time with me. But when he’s not around she never says that and I do my best to spend time with her but I will not tolerate her rudeness anymore I don’t need to get treated like that. I was bullied a lot by her mother , and saw her mother abuse her she’s currently living w my gram and I but my grandmother doesn’t discipline her, and when she goes to see her mom and dad she’s learning all these negative things from them like cursing, being violent, bullying others, she goes to a special education school bc she was too out of control and I’m sure she’s learning bad behaviors from other kids. I tell my grandmother take away her tablet and my grandmother last responded “ I don’t want to hear anything, you don’t know what youre talking about , I’ll have a talk with her later. She thinks talking to her at bedtime about how she behaved during the day will change her instead of disciplining her and correcting her when she does something wrong ASAP ....