Identify the skill set your daughter is missing regarding her inability to support her family. Is it because she won't get a job? Is it because she doesn't have marketable skills. The thing is that low-income families have tons of vocational options through state programs. Determining her deficiency may help her onto the path of self-sufficiency.
Unfortunately, Your granddaughter is going to be front row to the hardships created by her parents. Here is the great thing about hardship, it makes us strong. Hopefully, your granddaughter will make better choices seeing the mistakes of her parents. If you are in Tennessee, then you can lend moral support to your granddaughter and be the stabling influence in her life.