Who were the attackers?

"Umm, actually, Prince Elwin, I forgot to mention that I had an assignment due tomorrow. I am sorry, but I won't join you for arcade gaming today. We can try it some other day, perhaps?" Tianna smiled politely. 

She wanted to go, create some good memories with the prince, and let him know she was a good candidate for becoming the queen. However, when he asked Delilah the same question, all the excitement she felt earlier left her heart, leaving a cold sensation full of evil jealousy. 

"Well, in that case, let's reschedule it for some other day," Zephyr commented, but Prince Elwin couldn't say anything to rebuke the words. 

Tianna was like a ticket to bring Delilah along. And with Tianna's denial, he obviously couldn't seclude Delilah without his elder brother becoming suspicious of what was happening inside his head.