Venting.. Future MIL rant!

So she's not officially my MIL just yet but the woman drives me nuts!! I took my son to the park today so she can spend some time with him. (And so she gets off my ass about not seeing him. I'm a busy mom I do what I can!) The woman spent 20 minutes with him!! Then she gets all upset and mean when I wouldn't let her babysit him. Well one I don't trust her. She's given me multiple reasons not to. (Threatened me with prison twice because she didn't agree with child support.) And two if you ignore him while I'm around how can I trust that you won't blow him off if I wasn't around? Anyway, she met my son and I at the park. My fiance (my son's dad) was there too. She brings her other grandson with her. (Which is fine I mean my son needs to know his cousin.) The kid is about 4 and has spinabifida, honestly my heart broke for this kid. Well he's trying to interact and play the best he can (he can't walk and needs carried everywhere). My son wants to interact with his cousin but doesn't understand why he can't walk. Well my son decided to play by himself and try and get his dad involved. Every time he would try and play with his dad my future MIL would tell my fiance to play with his nephew. Like seriously wtf?! You don't and I mean don't separate father-son bonding! Then when my son seen his dad holding and playing with another kid he just looked so sad. My heart shattered. He hardly had any time with his dad because his grandma was shoving his cousin in his dad's arms. I give my fiance kudos for trying to spend time with our son. I just wish he would have stood up to his mom and chose his son for a few minutes. Oh and what really pissed me off is when her other grandson tried telling her that the noises around him were hurting his ears (he held his hands on his ears) she scolded him and told him he was being rude!! Okay no! He's not my child but it's still wrong! Scolding a child with special needs is downright wrong!! And she wonders why I don't want her babysitting my son. (*Side note* my son is afraid of his paternal grandmother. Has been since he was a baby. He's 2.5 now) Am I wrong for getting mad at his grandma for basically blowing him off when she nagged for this time with him? Or do you think I'm in the right here?

I'm posting anonymously to prevent any future problems.