Can a child be taken away?

A friend of mine got into a huge fight with her psychotic deranged ex, who is also her 6 year old's father. After she kicked him out of her house she was very emotional and was questioning her kid but was also yelling (she did not threaten, swear at, insult, or belittle the child), all she was doing was asking her what she said to him, but because of the emotions of the situation she was yelling. During this time her ex was standing outside audio taping her with his phone and is now threatening her with it by saying he will play it to the authorities. Whether or not he actually has anything on the tape is unknown, it could be inaudible, or just a bluff, but she is very scared that child services could take her daughter away. She is a very good mother who has made tremendous sacrifices in life for her daughter, and would not harm her in any way at all. Does anybody have any insight into the legalities of this or what processes has to happen before a child is taken away from it's parent. She is very scared, can anybody please help. Thank you!