Question

Hello Rabbi, I have a question:
"If a man lies with a woman in a seminal emission, and she is a slave woman designated for a man, but she has not been redeemed or given her freedom, there shall be an inquiry; they shall not be put to death, because she was not free."
This is talking about a 12-year-old girl whose father sold her to be a slave. They arrange a slave partner for her so they can multiply and produce more slaves, and then another scoundrel comes and lies with her (how much could a miserable 12-year-old slave want this or resist it?)
They flog her with a cattle whip and not him.
That sounds really unfair to me.
The possible answer that this fit the ancient world is not a good one, because the Torah is meant for all time, and so the question arises whether the biblical conduct is not moral. After all, it is a well-known principle in Judaism that it outlines morality and is the absolute moral truth, but here the story looks plainly unfair and immoral.