I feel sorry for your family, but thats already happened.
This is really true, if you are going to terminate her, better no leave the child with them alone. you wont know what she will do to the child.
If something happen like this to me, I will call the police straight away. Cold water to take a bath in winter, this is harming the child. I think that can be a good reason to arrest her.
Poor you and poor kid! They are very bad to little kids!! We always suffer from them. Try your best to protect your kid, she may do other things to hurt your kid