Catholics believe God gives us a “moral assurance” of salvation: that He will give us enough grace to live a Christian life, repent of sins, and follow Him into eternal bliss…provided we cooperate with that Grace. That element of free will irritate some “once saved, always saved” Protestants who, in their zeal to glorify God’s holiness and over-exaggerate man’s depravity, end up denying man’s role in his own salvation. They would conclude from our silence on “absolute assurance” of salvation (ie: whatever you do, you can’t lose your saved status) that we say, “Well, I’m PROBABLY going to Hell.”
Not so. We simply acknowledge that we retain our free will after entering a saving relationship with Christ, and the fruits that come from a living faith are necessary fruits.
Another angle that your Protestant friend may be going at: Do we Catholics believe God “destines” anyone to Hell? This is what is called “Double Predestination”, and it is a heresy condemned by the Church. Catholics believe that God wills all men be saved (1Tim 2:4), and He foresees who all will be saved. However, God gives each soul enough time and grace on earth to be saved. But he cannot force their will. If the person is adamantly opposed to God’s ways, God will not save them against their will.
You may say, “If God knows who won’t be saved, why does He not give that soul extra graces?” We don’t know how many graces God *did *extend to that person. All we do know is that no soul, at his own particular judgement, will be able to look at God and say, “You didn’t give me enough divine assistance to live your commands.”
God does not destine people to Hell where, no matter what they do, they are damned.