The reason why it's part 2 is because that's really when she was shown as a medical nin.
Read these pages on their healing abilities.
http://avatar.wikia.com/wiki/Katara#Healing
http://naruto.wikia.com/wiki/Sakura_Haruno#Medical_Ninjutsu Actually for Sakura start at the Chakra Control section...
I think Katara would win because she could freeze Sakura is a block of ice and she can bloodbend so Sakura would be beating herself up. There's more waterbending moves that could be used on Sakura, too. Plus, Sakura can only get you if she's close, Katara can do it from a distance. And she is...
You know the nickelodeon tv show, avatar, the last airbender? At the end, I'm almost certain that Katara and Aang are in love, so if they got married and had kids, I'm just curious...