I assume one is her love interest, though he is not deserving of a royal burial actually. The other two might be two of her sisters. They were six if I remember correctly.
Edit: Well, no. Three of the sisters besides The Duchess and Her Roseate Splendor are accounted for.
To me it sounded like one tomb is for the sister they left on the surface, one is potentially a tomb for their father (The results with the Queen say “and the words are of an old man, proud of his younger daughter.”, but the last one I’m not sure of.
Having played through the activity for the third time now, it seems like they have a very relatable sibling relation of a multilayered mishmash of appreciation and disdain. Not something I expected from these ancient forces. But I appreciate.