The story features an important reversal of modern times. Today, if someone said, "She's a Christian," it would mean a good thing, probably, but when the rumor gets started that Galina might be a Christian, the young men stand up for Galina, saying she is not repugnant or foul enough to be a Christian. The inversion of religious supposition invites a kind of second reading to the text, to see what else might be inverted in this way.
For one thing, a war hostage from the Ligians is treated by her house arrest family as a true daughter, and adoption goes a long way in Rome. Basically, to accept Galina as a daughter instead of a slave frees her future from absolute tyranny and abuse. That doesn't mean life is easy for her, but she is loved, and she keeps her nose out of trouble. So, when she is kept by Vinicius, Ligia (Galina) reels against his advances, for the man is an entitle predator, and she escapes.
Notice how all the men in the story obsess about Galina. Not only is she very beautiful, and perhaps exotic, she is also complex and fascinating, and her point of view is honed by her strange experience of youth. She is seductive because she is mysterious, but this ends up being something of an issue, because men use her as an object in their own fantasies of self-worth and power.
Secretly, Christianity is not what it seemed to the youthful lads. The novel even goes so far as to introduce a Biblical character, the literal saint and apostle Peter, in the flesh. Then in the aftermath of these strange, supernatural events, the claims of Christianity seem confusing and perhaps stranger than they had admitted at first. This pairs well with the original theme of the novel, the beautiful perplexity of mystery.
