Should i let my son grandma to his graduation

I am a 25 year old female with a 5 year old son. My son fathers mother has been acting funny towards my kid ever since her daughter had her grand daughter she start yelling at my kid mind you my son is a little different he rather stay in his own safe place. Fast foward to sunday i didn't want to go to her bbq she will always bring up that my mom send her like handpick her from heaven but my son wanted to go. My son father wanted to talk to me but everytime he tried to she say im not here to argue or that she talking to me so he can beat it they ended up having a big fight infront of my son where when she went to touch him he cried and kept asking me if we can go home. She been telling me to leave her son that he is a bum but she has the nerve when she with a pedophile and an abuser. Im over her after she scared my son to the point he doesn't ask to go to her house anymore