Is she sinful for avoiding calls from her husband's father due to his repeated, causeless ending of calls, and the negative health and psychological impact this has on her?

There is no sin upon you for what occurred between you and your husband's family. Rather, your kindness towards them and your overlooking their mistakes helps your husband in honoring his parents, which is part of perfect companionship. Your husband should strive to mend the relationship between you and his father with wisdom. It is permissible for him to convey words from you that bring affection, even if they are not entirely true, for this is not the blameworthy lying that corrupts relationships. Responding to evil with good brings affection and repels the whispers of Satan.