Is it considered unjust to a girl not to complete a previous engagement after three years and then propose to another without informing her, knowing that she entrusted her matter to God and was psychologically affected?

You are not permitted to curse the man, for he has not wronged you. His withdrawal from the marriage promise is not considered an injustice, and it may be for a reason, or without a reason, and there is no blame upon him for that. The matter of marriage is in the hand of Allah, and His decree is good for the believer, so be patient and do not grieve, for perhaps that is better for you. Allah Almighty said: "But perhaps you hate a thing and it is good for you; and perhaps you love a thing and it is bad for you. And Allah Knows, while you know not." (Al-Baqarah: 216). Increase in supplication that Allah may compensate you with something better than him, and say: "Indeed we belong to Allah, and indeed to Him we will return. O Allah, reward me in my calamity and replace it for me with something better."