She probably meant to take him in temporarily, since she clearly hasn't legally adopted him. They're all in a difficult spot, it's pretty clear this child is unwanted by everyone. Tia never meant to have this kid and probably only stepped up after feeling bad for him due to how terribly his mom treated him. She doesn't want to adopt this child permanently and it's likely she never did. Neither does OP. They're all in the right, they didn't have this child and it's not their obligation to burden themselves with unwanted kids. The only people to blame are his parents but it looks like they don't care anyway. The woman is just agressively trying to avoid putting a special needs, older child in foster care, but it might have to come down to that.