Can I just point out that in a run-of-the-mill comic or manga, all of this exposition would have been dumped on us in chapter 1 and never mentioned again? Instead, it is revealed to us piece by piece and interwoven with the subplot of Rachel and Elysia's establishing new framework for their relationship in the new world.
Seems like it was a relationship that she felt forced into by the kingdom, but both of them seem to have been treated like tools by the government in general.
Elysia has definitely felt exploited by the state back then, so much that she seems to refuse to acknowledge that Rachel has been just as, if not even more exploited. Methinks that both of them back then had realized more or less consciously that they were birds of a feather, enabling an emotional connection in addition to the purely physical act. And, as it turns out, humans are dumb creatures who can fall in love under any circumstances, if we spend enough time in physical and emotional proximity with each other.