Marona appears to wear her mother's earrings and father's headband (albeit, bunched up into a bracelet, likely because it's too big for her actual head).
She likely does this as a way to remember and honor them.
"....Hahahahahahahahahahahahahahahhahaha! Good thing he didn't press the SECRET button behind the throne, opening the SECRET passageway in the corner of the castle... where I keep the EMBARRASSING snapshot of Laharl at the CHRISTMAS PARTY!"
Fun Fact: The store in Disgaea, the Rosenqueen Shop, is actually named after Etoile Rosenqueen, from Rhapsody!
This means Etoile is so rich, that her family's business has spread into other dimensions (including real life, if you count the name of NIS' former online store...)