Is it considered forbidden to prevent the daughter of the first wife from entering the house of the second wife, knowing that the reason for the prevention is to protect the daughter of the second wife from negative influences resulting from discriminatory treatment by the father, especially since the daughter of the second wife sees her sister daily at school?

A wife has the right to prevent her husband's relatives from living in her private home, but she does not have the right to prevent their visits unless the visit causes harm. If it does cause harm, then she has the right to prevent it, based on the Prophet's (peace be upon him) saying: "There should be no harm or reciprocating harm." The husband should not cause harm to his wife.