How should one deal with the first wife's father who prevents her from returning to her husband after he married a second wife with her consent, and is it preferable to file a formal complaint against him?

A man is permitted to marry a second wife if he is capable of being just. It is not the right of the wife's father to scold his daughter for agreeing to her husband's marriage, nor is it permissible for him to prevent her from returning to her home. Rather, she must obey her husband and return to her home, even if her father is displeased. It is advisable to try and resolve the issue amicably and through the mediation of wise people. Otherwise, the matter can be taken to the Sharia judge to have the wife returned to her home.