Nezuko's Blossoming Flame: The Blood Art Of The Demon Maiden - Jhu Innovations
Her flames have a special property that makes them. Webnezuko's box is sent flying during the explosion, but uses her blood demon art to fall safely. Following the explosion, tanjiro realizes he no longer is withstanding.
I also feel that her being hypnotized by urokodaki helped her develop the bda into what it is today because of how she views humans afterwards.
