Is staying away from one's mother and avoiding speaking with her considered an act of disobedience, in order to avoid problems and altercations with her, especially if the mother causes continuous psychological harm?

The rights of parents and children are inherently obligatory, not conditional on reciprocity. Therefore, it is impermissible to fall short in showing kindness and benevolence to one's mother, no matter how much she might err, because her right is immense. Raising one's hand against one's mother is one of the most heinous forms of disobedience and is forbidden by Islamic law. Abandoning communication with one's mother is an act of disobedience if it harms her or leads to estrangement and abandonment. The questioner should weigh her words carefully and use kind speech, for responding to evil with good is the solution. If the relationship is very tense, silence might be better to avoid escalating the problem, provided that kind words are resumed once the situation calms down.