I think them being together is a sweet way of showing why Ze'mer is so strong. She still has the love of her life alongside her, supporting and encouraging her. Ze'mer is currently determined, but when the traitor's daughter dies, she gives up hope and transitions to the meek and feeble grey mourner.
One thing to note is that unlike all the other bosses spectators being shrouded in white light, the traitors child is there in the full. Meaning that they got the happy ending
All the intro/area/walkup themes are based on permutations and bits from in-game themes associated with the character! I'm happy to see it's appreciated
