How can I let my mother know the boundaries of a grandma because she clearly doesn't cuz she thinks…

How can I let my mother know the boundaries of a grandma because she clearly doesn't cuz she thinks grandmother means second mother! & it's pissing me off , for one I shouldn't have to ask more than once for my son back when I want him to put him to bed or just to have him period , she already talking about what food she is going to feed him for his first Thanksgiving as if Kai is HER son . ND I'm really not trying to blow up but I'm losing my patience very very fast with her ND we're going to end up fighting! She talking bout hurry up ND go to school so I won't be around because I wanted to put Kai to bed cuz he was crying. If she keeps it up I'll put him in the day care at my school so she don't continue taking on a mother role . When my patience runs out I'll become a huge bitch ND I'm trying for that not to happen.