All that Arabella knew about LucisNupta was that its main component was fairy dust. Fairies being the only species who could handle it, the latter is mixed in with other substances to snuff its side effects or any adverse reactions it can cause a non-fairy bride.
When all was said and done, the final result was an oil to be applied on the bride's hair, three nights before her wedding night.
She remained in dark about the details since the information only came to her attention through history books that spoke of vampire traditions.
Someone like Ada, however, who had procured knowledge in herbology and chemistry from her father, knew better.
She insisted on making and applying the oil herself on her friend's hair. Ada wouldn't have it any other way.
Eventually, Arabella just gave up and let her do whatever she wanted, trusting that she would have her best interest in the end.