Conversation so far:
when did diamonds become popular for engagement rings
In 1477, Archduke Maximillian of Austria commissioned the first diamond engagement ring on record for Mary of Burgundy. This sparked a trend for diamond rings among European aristocracy and nobility.
When did Mary of Burgundy inherit the Duchy of Burgundy
Mary of Burgundy inherited the duchy upon the death of her father in the Battle of Nancy on 5 January 1477
Where was the Dutchess of Burgundy born
Mary of Burgundy was born in Brussels at the ducal castle of Coudenberg

Question: How old was the dutchess when she received her first marriage proposal
Self-contained rewrite: How old was Mary of Burgundy when she received her first marriage proposal