What is the ruling on removing the hijab for someone who wore it under duress, and consequently suffered from depression and disliked her appearance because of it, while also fearing people's opinions?

The matter is easy and its solution is possible. Since you are convinced that the hijab is an obligation, wear it seeking the pleasure of Allah, not for your fiancé, so that you may earn reward and avoid the threat of punishment for those who display their adornment. Do not concern yourself with society's view, for the ultimate goal of a believing woman is the pleasure of her Lord. Seeking to please people is an unattainable goal and may incur Allah's wrath, as stated in the Hadith: "Whoever seeks Allah's pleasure through the displeasure of people, Allah will suffice him against the burden of people. And whoever seeks the pleasure of people through the displeasure of Allah, Allah will entrust him to people." If you wear the hijab for Allah, the matter will become easy for you. Turning to people in acts of obedience is a hidden form of shirk. The intention can be changed to sincerity by contemplating the greatness of the Lord and fearing His punishment, by associating with righteous women, and by continuously supplicating.