Buffy respected Katara. She was slowly growing to care for Katara in the same way she might care for her other girls, back at the castle. But Buffy suspected that Katara didn't have the requisite experience to understand how delicate it was to explain a death to another person -- especially when that other person lacked the requisite experience to truly empathize with a dead man (or woman) walking.

"Maybe...maybe telling her was enough," she suggested -- careful not to include herself in that enoughness. Like back on the battlefield, this conversation left them as confidants in the same shared secret. Not as helper and helpee.