She should TELL that POS daughter that SHE will stay home and care for her own baby.
If she's too weak to pull that off, then I'd suggest she make a pitch to DSS that the baby be taken away from the POS mother and placed in foster care.
If she doesn't want to see the baby placed in foster care, then she should attempt get get permanent legal custody and file with DSS and the DA to get child support from BOTH POS parents. If they can't pay child support, than after a few years she should petition the court for adoption and keep BOTH POS parents from even visiting the child.
Whatever course of action she chooses, she needs to deliver the old "Go, and never darken my doorstep again" speech to her daughter. Oh, sorry - I meant POS daughter. Far too many people let their adult children ruin their lives.
Write 'em off, like a bad debt.
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