Responses
Spoiler from another series, read with caution.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
Reminds me a lot of a spoiler from Who Made Me a Princess. Athy is original Athy, but she was reborn in the modern world with no memories, read book, and transmigrated into "book world". So the story we're reading is her 3rd life. But it seems like Who Made Me a Princess plays around with that idea much more than this one does, because it sounds like you got this info from an extra chapter, not a main story line chapter. Interesting nonetheless, thank you for sharing!

Spoilers from the extra chapters
It is assume OG Roxanna and the current MC are the same. Og died,reincarnated into modern day,"read book",rebirth back as Roxanna.
OG Roxanna was not as stong as current Roxanna and was a tad bit wimpy.He failed the test and her mom begged for her life. Years later she met Cassis fell in love with him,but was three months late.she asked to have him as her "toy".because she saved him to late, he was already broken and he was like a puppet with not soul. Even so sje cared for him and treated him very nice.she always regret saving him so late.one day while she wasn't with him he was killed by her siblings.that was the start of her revenge.
She met Cassis's sister at a ball or some party and started to manipulate stuff behind the scenes for Cassis sisyer to build her harem(just like in the book). She made a deal with the sister to let her mom live with them and let Roxanna deal with the Black family. After the MOm left, Roxanna summoned a demon and killed all of the Black family members.Her wish was that Cassis would be saved or something like that. Hence there was the whole idea that the Current Roxanna was OG Roxanna(mtl wasnt straight on that)