Tell your friend not to make presumptions about her step father. If her mother has chosen him, she might have considered all the aspects. Ask your friend, what if your mother start making comments about your her friends on presumptive basis? Would you like it? No, never. She would tell your mother to first meet her friends, know them and then make any opinion. Same principle applies to her also. Moreover, on what basis, you are saying that her father is good person? You must have observed his behaviour. Tell your friend to treat her father as a normal human being and then analyise his nature, attitude and behaviour. Also ask her, what she does not like about her father? If she is not ready to do, what has been suggested above then she needs counselling.