My aunties daughter out of control

My auntie is an absent single mother. She had her daughter in a very extreme and violent abusive relationship. She only left him because he tried to kill her while her daughter was down the road at her mums house newborn. She then met another guy who she has spent 5 years with. He also was abusive but her daughter thought he was the real father. The real dad lost all custody rights because he admitted to trying to kill her and other things and failed to do the anger management course so he lost all contact privileges.

Well her daughter saw the abuse in the house and when they broke up he continued to see how. Slowly she started refusing to go and she wouldnt tell us why but we kept telling her that it wasn't right to leave her with a man who we already know is physically and mentally abusive she wouldnt take it because she needed her time and she wanted her to have a father.

My grandparents are very involved with her daughter. They have basically raised her and while her mum has been in and out of her life picking her up when she felt like it.

Well now her daughter refuses to see him and we dont ask because it just upsets her. Well her mum has a new man and he started off so well being really involved with her and bring a really stable life to her daughter which she has never had being passed around person to person.

I told her they shouldn't have met so early because it was going to lead to disappointment if they break up. But she did it anyway and it was going okay..well now it's all changed. He doesn't want to be involved anymore and avoids her which means her mum is avoiding her because she is trying to keep him.

Which means her daughter is always at my grandparents house. Her daughter has a very serious behaviour issue. She is an angel at school the teachers number one student but at home she is completely out of control. She kicks and punches everyone and doesn't listen. She sits and waits by the house phone for her mum to call and if it isn't her mum she doesn't answer the phone. She throws things. Now my grandmother is 68 and has had two major strokes and my grandad is still doing 2 jobs at 70 to support himself and my grandma and my aunties lifestyle

Her daughter is fully aware her mum is at the pub and even knows the names of them. She hates seeing her mum drunk it really distresses her.

At this moment in time they cant even be in the same room with each other because they push each other's buttons and her daughter just ends up losing control and hitting a kicking her mum.

We have all tried to pick up the slack for her mother but it doesn't help. Children need consistency. they need love. my grandparents are too old to be doing this and I am heavily pregnant and I have a 17 month old I cant always be there to intervene when she is hitting and shouting at my grandma. She is 6 years old. I dont know what we can do.

We cant confront her mother because she turns around and blames it all on my grandma saying it's her fault and stuff like that. My grandma isn't the same after her strokes and cries easily and cant cope with confrontation and fighting So she avoids it.

It honestly upsets me because I don't know what I can do. I want to help but the only answer is if her mum gets her shit together and starts prioritizing her daughter instead of everything else But it will never happen. I worry about the future of her daughter because the psychological toll it must be taking on her will affect her later in life