What is the way to get rid of the feelings of despair, frustration, and resentment caused by intense jealousy of a cousin for having obtained the opportunity to travel and acquire Western citizenship, especially given that this was the questioner's fervent wish, for which she strived greatly but in vain?

What you are suffering from, namely jealousy and malice, is a result of weak faith and insufficient contentment with God's decree. If you were certain that all matters are in God's hands and that His actions are based on wisdom, Satan would not have been able to mislead you. What is astonishing is that your jealousy of that woman is not due to her surpassing you in something desirable or permissible, but rather in something forbidden: emigration and naturalization in those countries, which is a pretext for the corruption of religion and morals. So, make this tribulation a means to renew your faith. Abandon competition for worldly things, for it is destructive. Instead, let your competition be in righteousness and goodness, and in what brings you closer to God, as stated in Al-Sa'di's interpretation of the verse, "And in that let those who compete, compete" [Quran 83:26], meaning that they should hasten to eternal bliss through righteous deeds.