What should I do

I have something that I need to get off of my chest and thought that this would be the best place to do it.
Anyhow, my family and I just moved into our new home this past February. Since then my children have made friends with the children in the neighborhood.All about the same age as they are. All pretty normal for kids. But, my oldest daughter, she's 10, has made friends with a girl who I am afraid is going to become a bad influence. This girl is 11 and for now is generally a good kid. The problem that I am having is that this poor child is screaming for some attention from her mother and isn't getting any. In fact when her mom is confronted about a situation she walks away.

Ok, so here is the whole story. In this house there are 2 young adult males. One is the brother and the other is his friend. Then there is the 11 year old girl and the mother (when she decides to come home). For the most part this girl is being raised by her brother and his friend. But, her brother and friend are not even able to take care of themselves most of the time. They are always drunk or stoned from one drug or another. That is when they are home. This girl is left on her own for about 70% of her time. That means she has to cook for herself, make sure she goes to bed at a decent time and get herself off to school(which lately has not been very often). I asked her brother once why she had missed school and he could not give me any answer. The mother is the only one working, which I know can be difficult. But, when she is not working she is out partying with her friends until she has to go back to work.

This young girl is over weight and starting to develop very quickly. She has been wearing lots of make up and trying to get boys to notice her. She has recently told my daughters that she thinks the friend of her brother that lives with her likes her. When she was asked why, she said because he winks at her and makes comments. When my daughter brought this up to the mom she just walked away. This girl has talked to my daughter about running away and dropping out of school. She has plans to be a hooker for Halloween and the mom is ok with that. Maybe that doesn't seem that bad to most people. But, should an 11 year old really know what a hooker is? Her brother has taught her all he knows about drugs and she has seen it first hand. He says that is so she knows what it can do. I told my daughter that if there was adult supervision there the other night that she could spend the night. But, then I found out the boys were drunk. I told her that she is not allowed to ever stay there. The girl can come here. But, that's it. And my husband and I have told her the reasons why (in a manor that was appropriate for her age). That same weekend the mom told her that she was going to be on her own for the whole weekend. Her brother could go out of state if he wanted to and it wouldn't matter. I didn't find that out until much later. Had I known that was the case I probably would have suggested that she stay at our house for the weekend.

I don't want to tell my daughter that she can't hang out with her anymore because there really aren't any more kids in our neighborhood that are her age. And I don't think this little girl is a bad kid(right now). But, if her mom doesn't wake up she is going to be in a very bad situation. And I don't want to call DFC because the worst they would do is take her out of the home and put her in foster care. And I don't think that bouncing around from home to home is what she needs either. Her dad died when she was a baby. So, that option is out as well. I'm just not sure what to do here. I am trying very hard to stay out of it. But, it seems like everyday there is something new to add to the fire.