I absolutely hate when my mom acts like my sons mom. Everyday it's her telling him something or me…

I absolutely hate when my mom acts like my sons mom. Everyday it's her telling him something or me to do something. He's MY child. I gave him chocolate chip cookies and she points to him and says "no more chocolate for you" ummmmm he will have as much chocolate cookies as I wanna give him. Like wtf lol then yesterday I went to go to food line she talking about "don't get him out" she's my mom but I had to kinda tell her straight like know your place, you're the grandma and I'm his mother and if I wanna get him out of the car and take with me or if I wanna give him something sweet that's on me not you. She obviously doesn't listen well lol.