Don Dahlia is a human involved in the Nameless Slums Quest. She is suspected of trafficking in Phoenix Tails. Her house has several sets garish and fancy clothes about as well as a copy of Romeo and Juliet she has been reading. She doesn't seem to be able to cook very well though.
After Luka solves this case, she no longer sells Phoenix Tails from her tent and instead becomes a battle fucker but only after you pay her 1500G for a Ticket to Heaven. If Luka bests her, she gives him Thief's Knowledge and becomes available for recruitment as a companion. She does about 400 damage during BF.