I agree as well, Nate... to a point. The grey area on this is we don't know what "I don't think it's all one-sided" means (it could mean shallow flirting on the cleric's end, or it could mean he/she is on the verge of renouncing the religious order).
Unfortunately, religious devotion can run the gamut from good old-fashioned piety to all-out obsession. And having less-than-convenient attractions is a part of the life process -- it doesn't automatically mean this man/woman of the church has transgressed. This cleric obviously sees a spiritual argument for celibacy, and these spiritual beliefs aren't precluded by the natural impulses to connect with another person (even romantically). That is, he could be genuinely infatuated, but it doesn't mean a celibate path isn't right for him.
Also, since religion and culture are often intertwined, there's no telling the depth of this person's attachment to the church. A priest could give up the cloth, but feel immense guilt for abandoning a lifelong practice. Guilt isn't the healthiest thing to bring into a relationship (and in this case, it would probably turn to resentment).
As you say, this person chose a chaste religious order of his own free will.
Of course, this religious person could be having doubts, and these doubts could be manifesting into a possible relationship with Dalia's friend.
As a Virgo, then, I'm gonna have to claim the title of the one sign of the zodiac that can be practical and romantic at once. I think you can be both passionate and pragmatic. It isn't wise to run screaming for the hills just because a relationship seems impossible, nor is it healthy to carry a torch for someone whose beliefs/psychology won't allow him to commit to a relationship. The Virgo approach, then, might seem clinical, but I would say that for the friend in question, it's best she put it all out on the table-- feelings, hopes, expectations. It's up to the priest/imam/what-have-you to react and do with the information what he will. And then Dalia's friend can continue down her life fully informed and with no regrets.
(At this point, if the guy still shows reluctance to leave the religious order, I strongly urge the lady to cut off all contact for a while and move on. At that point it's just self-punishing to pursue somebody that embedded in a restrictive lifestyle, and she will have done all she can to pursue it. It's all very romantic to say love will find a way, but that presupposes that both people are receptive to it...)
Ultimately, it comes down to the choice the other person makes. In a way, it doesn't matter if the choice involves religious order, or choosing between two possible significant others, or relocating or any other huge choice that people in love are confronted with-- if the guy isn't willing to put in what she is, it's not an equal relationship.
Best of luck to your friend, Dalia.