It was no secret of how dangerous Adele is. Her eyes had spoken of her annoyance on seeing a human who she had seen lower than her had somehow managed to put her tail around Cassius. From what she had heard from Princess Marissa it seems that the royalties held a tradition of marrying cousin to the heir of the crown.
As Adele was deemed far too young for Cassius, their engagement was never solidified, unlike the Princess who had no choice but to be engaged to Lucien. To Arabella this was odd. From the village, anyone who marries their cousin was judged insane but it seems royalties were more focused on keeping their blood thick. While Marissa was unhappy with the union, it seems Adele wished that the union happen. Though not between Marissa and her brother, but rather between herself and Cassius.
Therefore the aggression that Adele showed to her for being able to attract Cassius' attention wasn't too impossible to guess.
