Lady in question is quite a well known kimono wearer and has a strong Internet presence. Her dress style - heavily influenced by how kimono was worn in the 1920s which wasn't as restrictive and formalised as it is now - was completely appropriate for the setting she was in until she took part in the tea ceremony demonstration. I cannot imagine she intended to take part in this.
Same person dressed as an oiran (courtesan/prostitute) for another event, hopefully she didn't attend another demonstration of a formal art in that guise.