Glad to see I'm not the only one who found her shady, but the question still stands, how the hell did she get the bracelet? Is she the daughter of the duchess? Someone who's using the body of the duchess? A secret twin sister of Ludville? Was the duchess pregnant while she was on that trip? Did the duchess cheat on the duke? Did the duchess survive and marry someone after the accident? What's going on here?
That's a lot of questions haha but as I read the spoilers given in the comments, the duchess fled. At that time she knew she is pregnant. The thing is, this is her way of protecting her family. She was a member of a cult and she was a spy sent to the duke and have a child with the duke and have the child's soul switch with a member of the cult. But Ludville have a protection, like a divine protection (?) that they couldn't touch his soul. Also it was said that the duchess ended up loving both her husband and son so she decided to run away when she knew she's pregnant with the second child. Since she believes that the cult will go after her again once the child is born. (Personally, I don't think that's a good idea at all but oh well, the author wins all the time.)
As for the bracelet, it was given to Rania by her mother (?) but they both killed 3 years before the start of the story. I don't know if they died together or if the duchess died first. Then Rania's body was taken by the member of the cult.
this au series is such a gem to read