How can I help this child?

She’s 14 and her mother is “going through” something. She’s my daughter’s best friend and my daughter witnessed her mother tell her she wished she had an abortion and never had her in her life.
The mom kicked out her husband (15 year old girl’s step dad) because he’s not working, however he had an accident at work a year ago, with three back surgeries and metal rods, is on disability and still not cleared to go back to work.

The mother told this child that she wants to “get rid” of her and ship her off to her grandparents house.
The mother had this child when she was quite young and we think that she’s resentful and is going through something of a ‘second adolescence’

The mother back-pedaled a bit this weekend and apologized to my daughter for saying what she did in front of her, but still hasn’t addressed this or apologized to her own daughter.

She’s a good kid. This young girl has been like a part of our family already, and I want to help her, but I don’t know how to approach this situation.