AGHHHHH THIS SCENE
So they’re sitting together and Usagi asks if she’s really going back and when Chibs says she is Usagi responds in a kind of dejected voice and Chibs seizes on that and is like “HAHA YER GONNA MISS ME!!!!” and Usagi’s response is “NO I’M NOT” and she stomps away, trying not to make eye contact with Chibs because she just can’t take it, BUT CHIBS IS GOING AFTER HER ON THIS,
So of couse they end up getting into a “WILL! WILL NOT!” bickering match because it’s them. Usagi, is of course, on an eight year old’s emotional level., But Usagi is getting so worked up over having to deal with this painful departure, OVERWHELMED WITH FEELING, that she once again deliberately breaks eye contact with Chibs and OVERSTATES TO THE MILLIONTH POWER HOW MUCH SHE WILL DEFINITELY NOT MISS CHIBIUSA!!!!
Chibs takes it to heart. She wasn’t just bickering to get a rise out of Usagi, she really wanted to hear that she would be missed. She and Usagi have worked through some things, but some part of Chibs still fears Usagi really hates her.
But of course, Usagi was just denying in a vain attempt to fend off THE WAVE OF PAIN Chibs leaving is causing her. She was trying not to acknowledge how much she will miss Chibs because it feels like it’s going to rip her apart. The fact that Chibs doesn’t see this and accepts her denial as truth actually makes her angry. “WHAT DO YOU KNOW. YOU CLEARLY STILL DON’T EVEN KNOW ME IF “WILL YOU MISS ME” IS EVEN A QUESTION FOR YOU”.