"Katara, what's the best way to get fresh blood out of cotton bedding?"
All eyes turn towards Aanjing, then drop to the balled up sheets she's holding in her arms. Instantly the kitchen is so quiet that the songbirds of the Inner Ring seem to thunder with each warble.
Sokka asks, "Whyyyyy?"
"Menarche. So, about the bl-"
Katara springs out of her chair and throws her arms around the younger girl, bewildering her. "Oh, Aanjing! What wonderful news!"
"What's men-ar-che?" Toph asks Sokka.
"Um, Katara can field that one."
"It means," Katara, flush with pride, declares, "that I'm going to cook up a special dinner tonight in honor of Aanjing officially becoming a woman!"
Toph lazily twirls a finger. "Whoopty do."
Keeping a close eye on her friend, the last airbender carefully asks, "And I wasn't before... why? You do know I have my arrow, right?"
"Aanjing!" Katara gasps. "You don't need to feel ashamed. A woman's first course is a natural, wonderful thing."
Aanjing stares back at her for a long moment, then relaxes. "This is a Water Tribe thing, isn't it? Like how you yell at me if I don't wear that whatsit when I swim."
"That's it!" The Avatar smiles. "I guess your people, uh, throw parties for stuff like a girl's menarche and a boy's first ejaculation-"
Sokka spits out his tea.
"-but the Air Nomads don't. So can we not? Please?"
Katara wilts. "You don't want to do anything special?"
"Honestly? I just want clean bed sheets and some ginger tea for the cramps."
"Cheer up," Sokka tells his sister. "You can always cook a special dinner for Aanjing's birthday party."
"...yeah! You're right, Sokka!"
'Birthday PARTY?' the Avatar mouths to herself, before deciding to stay silent. She'd crushed enough of Katara's dreams for one morning.