The difference between the treatment of males slaves and female slaves reflects the economy of the time, and were put in place so that the female slave would be provided for. As women generally had less options, the master had additional obligations before letting her go into the world, likely destitute. As far as being sold as a slave to begin with, to my understanding it would be for debt repayment, combined with betrothal. So in the situation where she was not kept as a wife, or given to the master's son as a wife, she was not to be re-sold to foreigners, but had to have been provided for or set free.
Either way, slavery in this country is illegal, because Christians pushed for that. They took their interpretation of the New Testament, and wanted to make it the law of the land. I'm not itching to get slavery back, I don't think too many other Christians are either. I therefore don't see the relevance of this passage today. If the passage is irrelevant, I don't see why it should push you away.