Is a suitor entitled to break off an engagement in order to marry another, and is the fiancée sinful for not forgiving him?

The engagement is a promise of marriage and is not binding on either party. If either party sees a benefit in dissolving it without harming the other, then there is no blame upon them. The suitor erred by leaving a Muslim woman to marry a Christian woman in the land of disbelief, due to the danger this poses to his religion and the religion of his children. It is advised not to dwell on it, to thank Allah for His decree, and to ask Him for His bounty with a better spouse than him. Forgive him if he wronged or oppressed, for Allah Almighty says: (So whoever pardons and makes reconciliation - his reward is due from Allah. Indeed, He does not like wrongdoers).