Is it considered disobedience for a daughter to live independently away from her parents, given that she suffers from mistreatment and restriction by her parents and siblings, their rejection of her engagement, and their deprivation of her right to work and personal freedom?

Your family may be mistreating you, but your parents have a great right over you that is not abrogated by their ill-treatment. We do not advise you to isolate yourself away from them. Rather, have some wise people speak to your parents to improve their treatment of you and to stop the harm from your siblings. It is permissible for a woman to propose herself for marriage to someone she sees as righteous, within certain guidelines. We advise you to draw closer to Allah Almighty, and to frequently remember Him and supplicate to Him.