Is a wife's boycotting of her husband's father, who attempted to sexually harass her, considered a severing of kinship ties?

In-laws are not among the kin (dhawu al-arham) whose ties must or are recommended to be maintained, unless they are also your relatives, such as an uncle from the father's side or an uncle from the mother's side. Estrangement between Muslims is forbidden, but it is permissible, and may even be recommended or obligatory, in specific circumstances, such as when communication leads to a deficiency in religious commitment or harm. Based on this, there is no blame on the questioner for shunning her father-in-law as long as she fears his bad character.