Trying to teach my daughter to stand up for herself

My daughter is 4 and the sweetest and MOST sensitive little girl ever.

She plays a lot with my niece who is a yr older. My niece likes to tease and get my daughter to cry. Especially by saying I’m going in the house or walking away pretending she’s not going to play anymore especially if she doesn’t get what she wants (we are backyard neighbors we put. a gate between our backyards). My daughter will start crying please don’t go please play with me and gives into whatever.

I’ve been trying to get to my daughter to say “if your not going to be nice I’m done playing with you” and walk away. Today my niece hit my daughter and my daughter pushed her down and said your not a nice girl I’m not playing with anymore. And she came into the house.

I asked my daughter what happened and she said My Grammy told me to hit her back if she hits me that she’s not a nice girl. 🤷🏼‍♀️

Now Im just waiting for my sister in law to call me and complain that my daughter pushed her daughter. she thinks her child does no wrong 🤦🏼‍♀️

- edit - my daughter has only ever hit once before this (that I am aware of) it was actually a bit. But she knows that we keep our hands/feet to ourselves. Like I said she’s very sensitive so she was crying bc she felt bad that she pushed my niece. We did have the talk about no hitting and I’m going to talk to my mother in law as well