Is falling in love with a Christian is haram?
Falling in love is an involuntary thing and Islam has no rules regarding it. Muslim men are permitted to marry Christian women, while Muslim women are not permitted to marry Christian men. Therefore if a Muslim woman falls in love with a Christian man, the falling in love in itself is not a sin, but she is not permitted to marry the man if she wants to remain a pious Muslim. Her case would be similar to a man falling in love with a woman who is already married.