Crazy grandma?

Question

So basically my mom, is one of those crazy overbearing grandmas. I told her I was moving to sippy cups on Christmas, she bought my son a new bottle for Christmas. Every time she’s around him she finds new things that I “need to talk to his doctor about”, things that I know are fine. Recently she told me his legs where crooked and I needed to tell his doctor so they could get fixed. We went to his doctors yesterday, she came with me, and after I told the doctor I didn’t have any concerns she butted in like “ACTUALLY, his legs crooked” the doctor told her it was normal because he just started walking 2 months ago and it takes time for the legs to straighten out. It was honestly so satisfying lmao. 
Anyway, after his appointment we went to MY grandmas house, my sons great grandma. And my younger brother who’s 16 was helping my son pull his pants up when my son fell forward and hit his face on the ground. My mom SCREAMED bloody murder and literally sprinted across the room to pick him up, started screaming names at my brother and tried to get me to hit my brother? I said no, I could tell it was an accident and my brother felt bad, so then she tried to get my other brother, who’s 15, to beat him up, and he was like no to her face so she reached out and hit him in the arm. Then she started crying and went and sat in my grandmas room with my son. Idk what to do to stop making her so crazy?!?
Edit: I’d like to add that my mom actually doesn’t have custody of either of my brothers, they live with my grandma. She lost them over drugs and choosing her abusive boyfriend. I allow her around because we only have 1 car and my SO uses it for work all day, everyday, and plus my SO thinks the whole “family’s more important, stop fighting” way, so she can literally do anything and he’d think it’s ok for her to be around because it’s my sons grandma.

Answer

Your poor brothers..is the having them beat each other up thing common? And same with the screaming calling him names?? If so, forget about crazy grandma issues, your mom needs to be reported to cps for child abuse.. those boys shouldn't have to deal with a psycho mentally emotionally abusing them while encouraging them to be physically with each other

Answer

I get the whole “stop arguing, be a family” thing. I had a very unhealthy relationship with my mother growing up- it was toxic. My husband always encouraged me to be the bigger person in each situation and not let her words & actions determine my outlook on others & in life. I don’t think we have a “good” relationship now, it just kind of exists. However, boundaries have to be set because actions, words, and comments will have an impact on your child (even at such a young age). Our first baby is due next week and I’m not sure how we will encourage the baby & grandmother relationship while also protecting his heart & mindset.

Answer

I get having only one car, but you need another solution. If she’s not allowed to raise her own children, why would you want her around yours? It is your responsibility to limit her connection to your child. 
When we only had one car, I got up and took my husband to work and then went and picked him up. I don’t know how long your commute is, but that may be what you need to do.
You’re the parent now. You cannot stop her behavior but you can parent your own child. And that means limiting who is around your child.

Answer

She's being crazy overprotective and overbearing because she lost custody of your brothers. You need to limit her with your child. Also NEVER take her to a dr appt again with you just saying.

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It doesn't sound like you're doing anything to trigger the behavior, so I don't think there's anything you can do.  But if this is a change in behavior for her (or honestly, even if it's her normal behavior) I think a therapist or psych evaluation might be a good idea. That's not healthy.

Answer

I’d stop being around her. You can’t change what won’t change