Although Katara had no idea what Sarah had done, exactly, she felt some sort of unexplained power unlike anything she was used to surge through her. It was so strong, in fact, that she had to actually let up on her hold over the werewolf lest she crush him into the unyielding floor on accident.
A gasp burst past her lips when the dart hit its mark and the creature's struggled began to lessen until, finally, it fell limp. Slowly, carefully, she brought her hands back to her side before stumbling backward a bit. For a few seconds she thought she was going to pass out but the power was still there. Not as strong as before, and not the same strength she drew on from the full moon, but it kept her upright and coherent.
Her gaze first went to Angel, accessing his injuries, then to Sarah, accessing hers. Finally, her attention landed on Zuko. Out of the three, he was the one who looked the worse for the wear. Yet it was Sarah who had given her this power and she felt wrong, using it on someone else before helping her.
So without a word she slid to the floor beside the blond woman. Water appeared on her palm and took on a faint glow as she gentle ran her hand across the broken arm.
"I'm going to help you," she said in a quiet, yet firm, tone. There was no room for argument in her voice and, this time, she wasn't taking no for an answer. She simply got to work, head lowered and gaze intent upon her task.
Normally, wounds that involved the breaking of bones weren't able to be fully healed with her waterbending. After all, water served as a natural healing catalyst, but bones took time to grow back together. That couldn't be changed no matter how much she might wish otherwise.
However, between the full moon, and the magic flowing through her veins, Katara was able to get the bone set properly and begin the mending process. It wasn't healed entirely, of course - time really would be needed for such a thing - but rather than take weeks upon weeks, if not months, she imagined it would heal fully in a much shorter time period.
Next, she turned her attention to the claw marks. Those disappeared within mere moments, being relatively simple even without all of the aid Katara had at the moment. Once finished, she gave Sarah a small, sad sort of smile.
"You should rest for a few moments, at least. You're safe here," she suggested before rising to her feet and, after casting a wary look toward Oz and then an unreadable one in Angel's direction, moved to Zuko to begin the process of healing him while she still had enough borrowed power left within her to do so.