Cuz when 7 was new to the neighborhood, 9 brought over some cookies, but 7 had been chopping onions when 9 rang the doorbell and 7 accidentally cut itself. So, when 7 answered the door, it was in pain, a little bit annoyed, and couldn't see well, all while still holding the knife. 9 set the cookie tray down and backed away slowly while repeating, "My name is 9, I have a family that loves me, and I'm sorry that I upset you." 7 tried to explain, but then 9 ran away screaming.
So, as you can see, it really was all just a misunderstanding, but 9 believes that 7 is mentally unstable and has a hair-trigger temper. 7 is worried about scaring 9 again, so it's considering having a conversation with 8 as a mediator. Just the three of them: 7, 8, and 9.