Claudia Jessie was 30 during the filming and playing a character presumed to be half her age at the time.
The Queen is actually snorting tobacco not cocaine. The show takes place about 40 years before the discovery of Cocaine.
Eloise and Benedict smoke a cigarette lighted with a match. The story takes place in 1813, but matches were not invented until 1827. A cigarette would have been lighted with a spill from a fire.