When Cassandra (Romola Garai) and Rose Mortmain (Rose Byrne) visit a luxury department store in London, the smell that impresses them the most is a bluebell perfume spritzed by a sales assistant. Rose establishes a connection between that smell and heaven, emphasized by the unusually posh place they’re at.
Later in the film, Cassandra and Stephen Colley (Henry Cavill) have the same conversation; it’s Cassandra who utters the “I can smell heaven” previously said by her sister. In this case, they’re not referring to the perfume, but to real bluebells.
Rose writes a letter to Cassandra, describing the preparations for her upcoming wedding to Simon Cotton. She speaks of her visit to the same luxury store she went to with her sister some time before: the place, she explains, has the same exact smell, “heaven and bluebells”.
Cassandra is over the moon when Rose gives her the bluebell perfume as a birthday present. This is a fictional perfume, but the label and the box remind me of Penhaligon’s Bluebell, an intoxicating perfume created by Michael Pickthall and launched in 1985.