It is not Aadya's fear, but the appearance of the Kanabō that moves Yuki to action. Aadya steps forward first, but she does not step forward alone. After all, Yuki was trained in fencing, and an armed opponent is a very different thing from an unarmed one, even if they are fighting with heavy weapons and not with rapiers. 

So Aadya steps forward to strike, and Yuki steps forward and to the side, her tail whipping behind her for balance as she crosses over her feet to slide around Aadya and bring her axe around in an arc designed to push the Kanabō out of the way and lock up the Dark Dragon for Aadya's strike.

Six years ago, this might have worked perfectly. A smaller, faster Yuki would have made it in under the dragon's guard, used the leverage she had from her rush, and a smaller Aadya would have been able to make the maneuver while effortlessly shifting herself to avoid Yuki. Today, this still might have worked if Yuki and Aadya had been in sync with each other and Aadya had been reading her friend's movements. But she had resigned herself and so when Yuki stepped in, it threw her off instead, causing a moment's hesitation and instead leaving Yuki to take the full strength of her second actual physical dragon she's dueled in Thellamie this time.

As she pushes past the stunned Aadya and flings herself at Sayanastia's Kanabō, she has time to only say one thing: "who are you becoming beautiful for?!"

[Figure out a person: 2+2+2=6. Yuki's only question on a miss is "Who do you love?"]