Perhaps the girl was not only adept with the control of water, but could also heal with magic. Xena was no stranger to magic, so that didn't shock her too much, either. She stepped forward when the girl demonstrated for her and nodded, but she leaned her staff against her shoulder and reached out to bend her elbows slightly.
"If you lock your arms, you run the risk of getting your arms broken. If there is no resistance, you could get an arm dislocated, or your elbow or wrist broken, but if you leave some room for give, you can protect yourself better." She nodded, then stepped back. "Try again."
She watched her try once more, and then nodded. "Good." She went through the motions of the defensive stance once more. "Now let's try to get you used to taking blows." She waited for her to get into the defensive stance before she brought the staff down on her own. She wanted to get her used to the vibrations, but not hit too hard. She wasn't ready for the full force of her strength.
She smacked her staff down on Katara's and then stepped back, waiting for her reaction. She did it again, and then again. Harder each time, but still not as hard as she could. "You are not always going to have an opponent who hits you where you expect them to hit. So you will need to anticipate their actions and be prepared to block it. You can switch sides easily with this staff, just move your hands to the opposite end as you turn."