If this was my son and my situation - after the time there was a problem I would have flat out told her that what she was doing was not the way I was raising my child and that from that moment on there would be not time with grandma alone and if grandma had a problem with that then no contact at all, and there would not be any waiting for things to calm down and or blow over. The reason I would do this is because I know that one situation causes as much damage to a child as accumulation of times. For example a person who gets called a name by a care taker once feels the same way a child who gets called that same name by a care taker many times. A child who experiences one abusive hit suffers the same emotional damage as many abusive hits over a space of time. A child who was molested once suffers the same emotional damage as a child repeatedly being molested over a space of time. So many times in my real world groups I have encountered survivors who say "oh don't mind me it was only once". and then I ask the person were you humiliated, scared, and so on? and they answer yes and then the person realizes yea it was only once but that once caused the same feelings. when any of us abuse survivors were / are in therapy when we tell of the only once situations does the therapist say - well it was only once so you are ok. Also in my public days I found out that a parson who puts any child in a situation where they know there is a risk of physical, emotional or sexual abuse and or neglect can be held legally accontable as being an accessory to the crime of child abuse.

Why should I go to jail and lose parental rights to my child for someone else not doing right to my child?

why should my child repeatedly go through abuse and or neglect?

Im the adult and my child is the child.

I am the voice for my child to ensure his safety and physical and mental welbeing.

The right thing for my child regardless of what I feel about the person harming my child through physical, sexual, emotional abuse and or neglect is that he not be subjected to being harmed in these ways.

So if this was me based on the fact that I know my child is not being cared for propery and has already suffered because of the first situation happening and that if I did allow my son to be back in that situation knowing full well there was a risk of abuse or neglect and by doing so I can be arrested, I would say thats it the first time supervised by the parents or nothing and not put any "for now" "for a time frame" on as a condition.