Ex is letting child party till 3 am help????

my hubbys ex is a nightmare, she parties alot and therefore everyone around her suffer. her poor little girl that she and my hubby share is 9 years old, and the ex throws parties and gets too drunk and just lets the girl do whatever she wants.. the child usually ends up ping out at about 3 am or sometimes even later..... i am so worried because the girl is becoming very snappy and is restless all the time. the worst thing is there isnt a damn thing we can do about it.... we tried speaking to her about it and all she responds is "its none of your business, she's on my time" .... how can you get through to this person????