Both Fairy and Nymphs value peace over war, at least that's what a book about the Four had continuously stated throughout its pages. For them seeking peace and harmony is within their blood and war something they tried to prevent, even at the cost of their life.
It was such an eye opening experience for Raiene to see that Ertellib didn't quickly state an official announcement of admitting their faults and hoping for an understanding of somesort. When clearly, there's nothing wrong with venturing inside the forest. Especially for Fairy and Nymphs, when basically it was within their nature itself.
Why did Ertellib have to prolong this matter and cause an uproar within its own territory?
"And why would Fussyorl side with Ertellib if it comes down to war?"