After failing at her quest to convince the luck dragon Hraesvelgar (sorry i had to say that cause he totally looks like he's from the never ending story)

why does ysayle get mad at Estinien for suggesting that they slay Nidhogg, since peace as failed and Hraesvelgar doesn't care that his brother destroys Ishgard then it's kind of foolish of Ysayle to still cling to the idea of peace? Especially after getting rebuked that she was Shiva reborn, i would think that she would be more inclined to want to fight the dragons. It makes me think that ysayle would rather have dragons destroy Ishgard rather than see them get slayed.