Do I report my cousin to cps?

My mom is a social worker here and she has noticed some odd behaviors going on with my cousin. My cousins name is Abby to make this story easier. So Abby got pregnant, the dad is extremely toxic and abusive, so once the baby is born Abby leaves the dad. I personally can vouch that he has threatened to kidnap Abby‘s daughter and kill Abby along with other threats and not to mention him calling the cops on her saying that she was holding their daughter from him even though in our state and unmarried father has no custody. He has also showed up in the apartment complex yelling at 2 o’clock in the morning because she was afraid to let him near her in the baby after his remarks of kidnapping the baby and killing her. She has gotten him for child support but I fear that she is not doing enough. My mom has made the comment that she is afraid someone is going to report Abby in the complex. I truly fear for my nieces safety and I know that when Abby talks to the father it has nothing to do with the baby they’re always arguing and he’s always making threats. He abuses drugs and I am just very concerned for the well-being of Abby and her daughter. It really concerns me that he could make those threats and she would allow him to come around just a short week later. What do I do? Please be nice I’m going through a lot with this