Grandma (my mother) is really frustrating me!

My mother lives 100 miles away. She comes to stay with us for 3/4 days once a month. During these days she looks after my 2 year old rather than him going to his usual childminders while I am at work.My son is very attached to Grandma. When she is around he wants nothing to do with me and screams, hits and shouts whenever i enter the room while they are playing. He even tries to lead me out of the room so he can continue playing with her. It really hurts my feelings and I am getting a bit sick of my mothers reaction. She spoils him rotten. He literally can get whatever he wants when she is there and of course that is why he loves being with her. He turns into a really naughty boy when she is there and normally he is a very sweet child. She brings out the worst in him.She intervenes when I tell him off for hitting. Constantly making excuses like "he's tired, he's a baby, he's hungry". We've come to blows so many times over this it is ruining our relationship.Its making me angry because its turning my nice little boy into a not very nice one and I am worried that the time he spends with her is going to negatively impact on him as he gets older. Am I making a big deal out of this? is 4 days a month enough to spoil him?She also doesn't put him down for a nap during the day when he ALWAYS naps for an hour in the afternoon. She went on to tell me last night that he doesn't need a nap anymore and i should stop doing it. I know my son and I know he goes into a meltdown when he is overtired so he does still need a nap. His childminder agrees. Its bugging me how she thinks she knows him better than I do. If I give him some food, she'll take the rest off his plate and say he's had enough even though he's still eating it.Earlier this week he dislocated his elbow (grandma was holding his hand and he pulled one way and she pulled another). When it happened he only wanted me and kept telling her byebye (his way of saying go away). When we got back from the hospital she said how she can see that we (me and son) now have a real close bond. I'm his mother of course we have a bond. I think in her head she believes only him and her have this "bond" and its really annoying me.Do i need to just get over myself? via /r/Parenting https://ift.tt/2PAO6xW