Waiting for Normal by Leslie Connor.

Fiction for the 5th and 6th grade girls about real-life situations. This story is developed in an understated style of writing. Mommers ( main character Addie's mother) is not an outright abusive mother. She is a neglectful mother, spending her time watching TV and staying out all night, preparing a huge pot of soup and then forgetting to buy any groceries. Mommers has recently gotten divorced from Dwight who has custody of their two daughters (the Littles). Addie has to stay with Mommers because she is not Dwight's daughter. Dwight comes to visit and bring the girls to see their mother and to see Addie. Her grandfather also tries to help Addie but she hides the truth. Addie tries to live as though her mother is doing what she is supposed to do. Unfortunately, this has happened before and there are flashes of those past times in the story. Eventually Addie's trailer home catches fire and Mommers isn't there.
A very well-written story that does not play on your sympathies but stands on its own stalwart legs, just like Addie, trying to make a way for herself.