A priest told my girlfriend that it is okay for us to touch one another intimately before we are married. Is this correct?
No. Jesus stated in Matthew 5:28 that a person can commit sins of sexual impurity even in his thoughts. He stated, “But I say to you that everyone who looks at a woman lustfully has already committed adultery with her in his heart.” The same thing is true of fornication (premarital sex).
Looking at a woman to whom you are not married and indulging in lustful thoughts counts as committing fornication in your heart. If indulging yourself in mental lust for a woman to whom you are not married counts, how much more will intimate touching, in which you partially act out the sexual desire you have for one another.
Though some priests may not like to say so, fornication is a grave (mortal) sin. The apostle Paul states, “Now the works of the flesh are plain: fornication, impurity, licentiousness . . . and the like. I warn you, as I warned you before, that those who do such things shall not inherit the kingdom of God” (Gal 5:19-21). This is a severe teaching. It is one many unmarried people find hard to accept, but it is the clear teaching of Scripture, and we must hold to it.