Is a wife's refusal to communicate daily with the second wife who harmed her in the past considered Haram (forbidden) or a sin, especially given her feelings of discomfort and lack of trust towards her and her husband, and the absence of justice?

If the other woman was the cause of the husband leaving his wife in a state of suspension, then she is sinful and unjust. It is not permissible for a woman to seek the divorce of another [woman] in order to marry in her place. If this woman shows remorse and apologizes, her apology should be accepted, and she should be asked to mend what she corrupted between the spouses. There is no harm in communicating with her if her harm is not feared; otherwise, there is no sin in not communicating, as it is permissible to abandon one whose harm is feared. It is advisable to work on mending the relationship between the spouses through reconciliation, and people of goodness can be used as mediators for that.