I would say, let it go. She doesn't want this, respect her will.
Even the greatest saints had instances in which they couldn't realize their most cherished dreams. I will give you examples from another area than dating and marriage, but you will see the point I'm trying to make.
St. Francis of Assisi wanted to convert the Sultan of the Muslim army, and the Sultan came to love and respect St Francis after meeting him. Nevertheless, the Sultan couldn't find the courage in his heart to become a Christian and a traitor in the eyes of his Muslim people. With great sadness, St. Francis accepted the Sultan's decision and returned from the frontlines of the Crusade to his homeland of Italy.
Also, St. Francis Xavier, the patron saint of foreign missions, had a dream of evangelizing China, which he never accomplished. After baptizing many people and successfully spreading Christianity to places such as India and Japan, he became sick and died at the shores of China, before he could reach the mainland. See:
Apparently, God had a different plan and for reasons known only to him, he did not allow St. Francis Xavier to bring Christ's message to China.
Our late Pope John Paul II had a burning desire to reach out to the separated Eastern Orthodox Churches and especially to Russia and its people. The suffering Pope of Fatima, who was shot several times at point blank range by the asassin Ali Agca, hired by the godless communist Soviet power (through the Bulgarian secret service), almost died on May 13, 1981, an anniversary day of the first Fatima apparition of Our Lady (apparition of May 13, 1917). Pope JP II credited his miraculous survival to the protection of Our Lady of Fatima. He went on to consecrate the whole world, and especially Russia, to Mary's Immaculate Heart in 1984, and communism fell and the Soviet Union was dissolved in 1991, after the prior liberation of Eastern Europe, including the Pope's homeland of Poland, in 1989. A tremendously successful Pope, instrumental in releasing the Russian people from the yoke of communism, greatly respected by world leaders such as Ronald Reagan and Mikhail Gorbachev, yet he never realized his dream of visiting Russia, the Russian people, and the Russian Patriarch. Although this Pope had nothing but love and devotion to Russia and its people, its atheistic leaders tried to kill him, and even the Russian Eastern Orthodox Church hated him without a cause, so much so that the Russian Patriarch refused to ever meet Pope John Paul II during his lifetime, either in Moscow or at the Vatican.
These are all cases in which human free will (that of the Sultan, of the Russian Eastern Orthodox Patriarch), or God's will (the sickness and death of St. Francis Xavier, at the shores of China) prevented otherwise well-meaning and good, holy people from realizing their dreams.
So, let go of anxieties, and trust God with your life. This girl, for whatever reasons, chose a different path than the companionship she shared with you for a time. But this is not the end of the world for you. Trust God, he will take care of her, and he will also take care of you.